meta_notes:
I haven't played Sword Coast Strategems Insane Difficulty through BG1 for years - probably around the release of the EE, and haven't played a PC-Imoen duo ever so it felt like quite a fun thing to do (and it was.) Cloakwood mines were definitely one of the hardest parts because I was so (deliberately for RP) poorly prepared - once I had wands of fire and an amulet of missiles for Imoen + 1-2 sets of boots of speed the whole thing becomes a bit of a cake-walk - the PC character barely cast any spells in combat once I got to BG because the low cast time on wands of fire is just so OP. The only problem was not having a fighter to deal physical damage making quite a difference - but having two characters, rather than solo meant that one of them could kite enemies around while the other did damage with ranged - at low levels I also used the familiar a lot to deal damage to held/sleeping enemies and kite. Dust Mephit isn't pseudo-dragon level but its not useless. On later fights wands of monster summoning ogres can be very effective, though its a crapshoot as to what you actually get when you use it (hobgoblins no thanks).
I enjoyed the gnome cleric/illusionist, though obviously its up there in the most powegame-y combos due to the specialist mage extra spell slots meaning it gets more spellslots than any other class combo and the shorty saves with high con meaning it can tank spells unbelievably well even without magic resistance. Imoen was pretty weak as a pure thief (imo) - she only gets two two traps, which are useful, but her thac0 remains high enough that backstabbing can be a bit hit and miss - though great when it connects combined with a stack of invisibility potions and a pre-buff of strength. I put her skill points in open lock, set trap and detect illusion (for SCS BG2 really) - I'm planning on shadowkeeper fiddling with her as a thief dualed at level 11 to mage lvl 1 for the start of BG2 which I kind of think is fair considering I had taken her to lvl 10 in BG1 as a thief. I want the maxed Detect illusion (SCS crucial imo), set snare and open lock (find traps is not all that important imo since PC has the spell equivilent, a waste of thief points) and lvl 11 should be when she gets 3 poisoned traps which I am hoping will be fun plus an extra weapon pip for longsword (I like traps even without abusing them and her two traps per day in this run were a very useful bit of extra damage in a lot of places). Obviously with an oil of speed, potion of power, boots of speed, shortbow and a stack of arrows of detonation that's 3 fireballs per round and ridiculous move speed so its not like she can't be super op - and she can use necklace of missiles too.
As far as game time and leveling went durlag's tower took about 12 days of in game time but lots of that was travel to Ulgoth's Beard, then the tower then back to Baldur's Gate. I didn't rest all that much in the tower, but I did powerword:quickload a lot - there was so much that I have forgotten about the game, and about SCS which has also changed since the last time I played (I think). Durlag's allowed me to get up to level 7/7 on Arwen and level 10 with Imoen just by running through it - 4000XP greater dopplegangers and the like quickly add up the XP. Additionally, there is a very real change in power from Cloakwood to Baldur's gate because of the access to Sorcerous Sundries and the Potion Shop with a huge stack of gold, plus gauntlets of ogre strength with slings (PC only has 1 attack per round base but it does around 13 damage per hit) - the whole game shifts to blast mode at that point.
As far as the diary thing went, I tried to show Arwen growing up from valley girl moron to a more serious murderouspower-hungry neutral evil character who loves her sister. Mileage may vary, its very stupid.