I have no idea what you're talking about because none of that is true, I think you're getting yourself confused with another game.

BG1 lets you explore all adjacent/conecting maps outside of Candlekeep in any order you please, including going to maps with enemies a much higher level than you. It's why when I played it and others played it and we compared our playthroughs, ALL of them were different, because I hung around the forests grinding and exploring and fighting bandits, gathering their gear and selling them at the local shops. Others followed the story through as a linear pathway, and some also deviated to find teammates.

Bg2 is the complete opposite -- it hand-holds you through the story and streamlines the side-quests to avoid what happened in BG1, where you could breeze through the main story and end up being too low level to fight Baal at the end, where he will one-shot all of your teammates. BG2 makes sure you have enough side-quests completed so you're close to max level by the time you fight Irenecus or however it is you spell his name. There are a lot more story quests in BG2, but you don't have as much freedom to just go exploring the map as you please since a lot of the places are locked behind story progression.