Thanks for the reply. The mod is found here: https://forums.beamdog.com/discussion/82463/mod-bg1-npcs-for-soa-tob
It basically allows BG1 companions to continue into BG2, and also introduces new quests and banters. To my knowledge, it doesn't affect anything like stats, items, or kits at all. It allows you to "find" your old companions in various locations in SoA and gives them new dialogues, banters, and quests. I've grown pretty attached to some of the BG1 companions and want to continue with them if possible, and I'm kicking myself that I missed it in my original install.
Based on what you've told me, it seems that installing the mod will be okay. I'm still in BG1, so I haven't encountered anything that the mod would affect yet. And again there are no changes to kits, stats, or anything like that. I'm just worried that installing an NPC mod this late in the install order will ruin EET unless I go through the arduous task of removing mods in my list, especially since typically NPCs are really early in the install order. My EET install with SCS and all the other goodies was a hairpulling experience that I definitely don't want to repeat if I can help it.