While many years have passed since my last playthrough of the original edition, I do remember installing:
1: The banter pack from pocketplane. I don't remember the mod being particularly immersion-breaking but its been too long to really remember the details of it.
2: The unfinished business mod. This just adds some cut content to the game aka no bad fanfic quests, just some nice extra things.
3: The ascension mod. Only mods Throne of Bhaal, but it is an all-round improvement of the expansion pack by a significant amount, created by one of the design directors. It does make the expansion significantly harder though.
4: The tweak pack, whatever its called nowadays, has a lot of optional changes that I'd recommend. In particular shortening the time between NPC banter so you get to actually see some of the rarer conversations. It has a lot of nice things.
Of course there are also plenty of other optional AI fixes and various extra quests/campaigns/NPCs if you want them, but I'd not really consider it important for a second playthrough. The NPC mods tend to suck, but there are some good quest mods out there if you really want some. Just try reading some descriptions and see if they catch your fancy. Just to make it clear, I only played the original edition and don't know if the "enhanced" edition breaks any of these or if some of them aren't updated properly to work with it.
The mods aren't exactly hard to install, but do make sure to install them in the correct order as is mentioned on the forum post you linked. If I could do it as a dumb teenager, you can do it now.
