What do you consider "reasonably affordable"? Do you want a laptop, desktop, or don't care which?

If you want to stick to Mac, then just go to apple.com, or their physical store and check your options. There's not a lot of choice with Apple, aside from how much you're willing to spend. Their retina displays are great. Don't get a model released within 2 months, Apple is notorious for having serious defects on brand new models and trying to make the customer pay to fix what is Apple's fault.

Apple has closed it's ecosystem. If someone wants to release a program for OS X, they need to register with and regularly pay apple for the privilege of being on their operating system. They also no longer support OpenGL, which every other computer supports for communicating with graphics cards. This means for many developers, it's not worth developing for Apple. If you mainly use products from large companies like Apple, this might not be an issue for you.

Apple is non-upgradable. They solder everything to the motherboard, or include it in the M1 chip. Don't think that you can just increase the RAM later.

If you go for a non-apple laptop, you'll probably want an ultrabook. They don't come with powerful graphics cards, but they have 4K screens. The best for you would be a IPS HDR screen. IPS has the best color of screen panels, and HDR is 10-bit color. 8-bit is the old standard of 256 levels per color channel (R, G, or B), while 10-bit has 1024 levels.

If you want a touch screen, make sure it is listed. If you use a tablet pen, none will feel as nice as the Apple pencil, but they should still work.

AMD Ryzen processors are cheaper than intel.

There are a variety of weird or different tech offered by different brands. Some laptops can plug in external Graphics cards. Asus has a "duo" brand of laptops which come with an additional screen on the keyboard side. Gigabyte partnered with Microsoft for AI-enhanced ultrabooks that perform better if you absolutely don't care about privacy. On that note, if you get a windows computer, there are quick ways to disable much of the spyware Microsoft includes with their malware of an operating system. Mac's not as bad there, but it does report every app you open to Apple to get their permission to open it, which was found when Apple servers went offline sometime in the last two years.

If you have a costco membership look into their dell prebuilts.

They have "workstation" class systems at reasonable price with strong specs and video cards.

They tend to be short on storage so add on the cost of a 14+ tb spinning drive fir media and a 2nd ssd for gaming. Requires messing with a famously tightly packed dell case so also add the cost of paying some nerd to do it for you if that isnt your thing

Haven't looked at windows or linux for years, but they were horribly offensive to the eye for decades. Also 'going wrong' quite often, especially with OS updates. The user interface itself was the definition of ugly, and the linux guys were all about spending hundreds of hours trying to get it to work.

The main question there is how much can you afford to spend? Sounds like a top of the line Mac is what you need, but those can be as expensive as it is to live on the California coast.

Recently lost the last two years of my life when I finally dropped my android phone. Really sucks to lose all your data, and I sympathize.

Good luck with whatever you decide. FrostedCricketFlakes has excellent info and advice in his comment!

Sorry if I don't reply for a bit, people who have helped me out thus far (and ongoing)...

I've just been trying to do my own research, and it is... Exhausting, quite honestly.

Shit like this was so much easier (where I am), even a decade ago. Now it's "Nah, fuck you, sort out your own shit", which, for someone like me (i.e. a complete amateur) fucking sucks shit... :-/

Grumble Fuck this country (Straya), quite honestly...

You're used to mac and not building your own computer so get a mac.

Big thing is to get an M1 processor mac with at least 16 GiB or more memory. These are absolutely a must, so no buying a used old Intel for cheap -- not worth it at any price. The other specs won't really matter much for you, but upgrade if you feel like it.

If you're on a budget I'd get a Mini or Air expanded to 16 GiB depending on how you want to work. These will be fine for anything you're going to use them for as long as you get 16 GiB ram not 8 GiB.

Your main concern is storage space. Apple storage is ridiculously priced so get the minimum SSD and a cooled, external enclosure and normal huge spinning drive in it for a Mini or probably better with a NAS network attached storage for a laptop (so no wires). You can just pick pretty much anything that looks okay on Amazon. Normal hard drive has to be formatted HFS+ not APFS and will be fine for your use case. Get another external drive and set up Time Machine so you don't lose files again. You can get a huge storage and backup for a few hundred dollars. An unlimited online backup like Backblaze is a good idea at ~$70/yr for peace of mind or spend $100/yr on a new hard drive and keep lots of backups - once you get into many GiB online backup slows down and takes a long time to finish uploading, but you leave in on and it eventually gets everything.

I would avoid the iMac because it's all-in-one and not repairable, so when the internal drive fails it's junk. Maybe you can use it as a monitor, idk, but to me it's just an annoyance and not worth it.

A few things I've found spec-wise as someone who does a lot of photo editing at times. You want lots of RAM. Don't even consider something with less than 16GB. If I were going for longevity I'd want 32GB. Not that you'd necessarily need that today but you seem like me in that this will be something you want to have for a while. Particularly if you're buying a laptop since upgrades are not likely to be do-able. That's what I've found at least with software like Lightroom is that once I start opening up and editing a few different photos the RAM is gone in a blink. The good news is I don't notice photo stuff to be that hard on graphics cards...they use them but to a fraction of what gaming does. If I had to guess a lot of the stuff you mention is CPU heavy. That's a lot easier to get in a laptop form factor.

I've always been a fan of the Thinkpad X1 series, but a lot of this depends on what you want. I like thin and light over all, because I'm really a desktop guy at heart and if I'm buying a laptop it's because I need to move it around. I've had my hands on Dell and HP models and I wouldn't be afraid to buy one of those either. Although you're going to have to spend into the high-end to be happy with it I think. The low cost models I find either skimp on specs or build quality and you can't get both for cheap. I've got some PC gamer friends with something like a CyberPower or one of those "gamer" type companies and while I think they are good specs they are absolutely massive and clunky and it would be a cold day in hell before I'd carry that around all day.

Suggestion for your terabytes of photos that's sort of extra to this...look at archiving on discs. I don't really like to trash RAW files ever, but even my 20MP camera is burning up 25MB per file. If it's some sort of event like I did an F1 practice day where I'm doing bursts, it burns through the GB like it's not there. I started using a blu-ray burner and 50GB/100GB discs to archive things that I want to keep but don't necessarily need instant access to. The USB burner and discs in sleeves all together is like the size of a small book and I've got probably 2 TB of stuff stored like that. Keeps me from having to spend money on more hard drive space and high quality discs will outlive me.