Well, i finally completed a full BG2 and Tob playthrough 
. I installed only corrections mods, tatics encounter and ai (SCS2, BP, Improved battles, some tactics battles) and some tweak that i really love (Atweak, item and spell revisions, rogue rebalancing and refinements). I used a monk as my main character, solaufein, keldorn in SoA replaced by sarevok in Tob, Aerie, Kelsey, Nalia in Soa replaced by Irenicus in Tob, and decided to play on core rules.
The first thing that comes to mind is the fire giants : these are the ennemies that gave me a very, very, very hard time ! I encountered the first two fire giants in WK (before going to spellhold) and i have been reloading quite a few time before managing to defeat them. In fact i wonder if i don't have a bug : a lower fire resistance spell is launched at my party at least once per second 
(which basically makes my fire resistance goes from 125 to -175 in a few seconds, and my fighter kills himself in a round by their fire shields when attacking). Is this intended ? The only tactic that worked for me was to send one warrior with fire resistance, a potion of magic shielding (for the save), a protection from magic weapon (ability of the mace of detonation in IR) and using the wave halberd (which slays fire giants ona failed save 
). In ToB, i sometimes used my mages to beat them, but you need greater malison, a few lower resistance, and at least a few Adhw (6 at the same time seems to work...) for each giants. By the way, in Yaga shura's lair, my adhw didn't worked at all (i used a time stop with chain contengency of 3 adhw for each mage after lowering their magic resistance, and no fire giants was down...). This made the Yaga Shura's fight at the siege camp really hard (i used improved invisibility to avoid fire giants).
I really liked the sendai fight, although i used a unfair tactic : i sent my monk against the "main" sendai to block her, being immune to most of her spells. Maybe she should have a teleport spell to go after a weaker character.
The abazigal fight was quite hard also, with wing buffets sending your protected characters away and the dragons going after the other one, whith their breath sometimes one-shotting my main character (150hp and i only played on core rules...). It was quite a surprise also when you come back to his lair with the rope 
(i wasn't prepared at all and didn't rest before... )
I did a couple of reload on the eclipse fight : the main difficulty was to isolate the character without protection from magic weapons because the 2 first times, they went right after my monk, killing him in the first time stop, even when i summoned creatures in front of them,. I was lucky enough to have the 2 fighters going after my sorceror at one moment (who was using his fire shields and PFMW) and my monk being invisible in a corner.
The final ascension fight was quite difficult : during ToB, Aerie left (because i allow irenicus to have sendai's soul), so i took jaheira who left for the same reason.. i ended up with Haer'Dalis (yeah i had no cleric at the end, and no thief either...), and then the fight begins with Bodhi, Imoen in slayer form and Demogorgon. Not thinking ahead, i stupidly unleashed a torrent of spell at a marilith to prevent her from killing haer dalis 
(and with no sucess) which left Irenicus very few spells. As for the last stage, i sent all my characters (only 5 at this point because Sarevok choosed the wrong side 
) to one of the platform. I didn't know if this is intended, but neither Illasera nor Sendai followed me (Sendai was casting protection spells while i run away and I was out of Illasera's field of vision).
One of the fights in SoA i found difficult was the final bodhi confrontation with undead solaufein. I was forced at this point to left most of my characters in the corridor which was blocked by mordenkainen's sword. I went after bodhi first, then retreated in the corridor and took care of Solaufein with ranged weapons until his time stop triggered. I don't know how to take care of this fight without this tactic (one of my problem being i think that none of my character was proficient with the mace of disruption).
I had very few bugs in my game, one was that i couldn't talk to breudayael from improved asylum, i couldn't see his selection circle because he was casting again and again a spell trap improved insibility each second ! So i coulnd't try this fight. A few ennemies were also standing still during some fights (i remember captain haegen in the begining of SoA).
Orevall it was quite fun to play these mods. I really liked item and spell revisions which nerfed a few items, making some fights harder. I didn't used the items from the tactics mods ennemy because some of them are really overpowered. The atweak mod is also one of my favourite (revised fiends is a must !) If i had to reinstall, i think i will skip only the improved fire giants component (and in fact, looking at my weidu log, i realise that i installed both the improved fire giants from revised battles and the tougher giants from tactics, maybe this explains my issue with them).
A big thank to the community and to the modders for their fantastic job because it is well deserved ! 
Now i'm thinking of either soloing it (well trying at least to...) or playing with a different party. What are your advice ?
PS : sorry for the long post