Returned to playing BG2 after nearly a year, liked aVENGER/Wisp's mod a lot. Currently just done with Ch 2.
Undead: Shadows, wraiths, spectres etc. seem weak and unable to hit my party. Maybe change their attack to a touch attack (since they're incorporeal) with +4 to hit, base damage type changed to none, dealing pure magic or magic cold damage.
Since wraiths and spectres are incorporeal, maybe give them the ability to "vanish" into the ground and re-appear behind your party's front lines (...just a delayed dimension door, in engine terms).
The temple ruins (Umar hills quest): The undead here could really use an upgrade (same idea as the other "more sensible x encounters"). The random spawns might be quite hard (depending on level and installation) and SCS improves the Shadow Dragon and Shade Lord, but everything else is kinda pitiful. For instance, the "ambush" at the bridge is just some shadows and weak shade wolves, the unique shadow (RNGSHA01) who's in the cell and will be fought alone by the party is no stronger than a regular shadow. There must be some reason that shadow was dangerous enough to lock up...
Elementals: The earth elemental that SCS adds to the druid grove is replaced with an elder earth elemental, it can still be fought with a 8-9th level party but its earthquake is hard to defend against if you go here straight after CI as most people do.
Aerial servants are worth 9000xp, I'd think only enemy summoned servants should grant xp (via death script), even if it isn't the mod's purpose to "police" exploits. Edit; just checked and it looks like all summoned elementals are worth xp.
With SCS the enemy summoned elemental princes (DW#ESUNN, DW#ECHAN and DW#EZAAM) don't seem to benefit from the component to increase the HD of elemental princes.