While 5-6 party would be nice, I can do with 4, provided they offer something to balance out the group. While 4 characters is the 5ed standar, you are also supposed to have 1 character for each role. So a group with both Gale and Wyll is unlikely to work, since both are arcane casters. The balance breaks even more if the MC is also spellcaster.
I've read that Larian planned for 8 origin characters that double as companions. That would be nice if that doesn't detract from the custom character story and if there are no incompatibilities among companions. I mean, right now it seems that you have to choose between Laezel and SH, because they don't get along. But if that is the case, someone evil who wants a healer and a tank, might have problems.
Also, I hope that if companions options are limited, they offered chances to make the evil companions be able to work with good chacters and conversely, good companions being able to work with good ones.[...]
While the gameplay can get a bit more repetitive with multiple of the same classes, it still works. Gale + Wyll + PC caster + Other is a perfectly fine party composition. The other could be a fighter or a rogue or really anything. 5e has a much lower focus on class-specific actions (e.g., all classes can pick locks) and BG3 further reduces these differences through the prevalence of consumables and magic items with spell-like abilities.
Lae'zel and SH totally work in a party together. They banter and snipe at each other because of their dislike, but that can be amusing to watch. I could very easily see their relationship becoming more friendly, or at least more respectful, as the game progresses to later acts.
