You can't have two very different modes in the same system with a lot of problems, or a metric ton of work to overcome them. Arcanum ended up with many weird quirks and imbalances trying to make it happen on a smallish budget.
Arcanum isn't a game that will top any 'best games of' lists, because it's so eclectic, clumsy, and flawed - but it will still be the game that many hardcore fans of the genre hold up as special.
BG1-2 is probably the best "do everything pretty well" spokesperson title for that period of CRPGs.
Don't touch the idiotic enhanced editions, just spend 20 minutes installing widescreen mods and the fan bug fixes and get to it on the vanilla. Do you want to play the CRPGs that became classics with a minimum of modern conveniences, or do you want to play some version messed with 20 years later by a bunch of people, many of whom who have never made a good CRPG before, who just wanted to sell it for twice the price?