Regarding multi-class combos involving wizard, are scrolls for key spells, such as lightning bolt and chain lightning, even in game?
Yes, and the bad part is any class can use them, including martial classes, which makes casters pretty weak as you can just bring Shadowheart with a couple of martial classes that do immensely more single target damage and still have Fireball/Lightning Bolt/Chain Lightning/Cloudkill they can cast for aoe.
The game tries to balance by making scrolls very expensive, but stealing is so easy in the game that you don't even need gold.
Martial classes are just busted in this game. The worst classes are ranger and druid since they don't even have more than a single dedicated very rare/legendary armor that works with their class mechanic and they're just hybrid garbage that doesn't work well in a party combat game where specialized roles excel. Bard follows them but at least Otto's Irresistible Dance is a super broken CC spell that works on most bosses and stunlocks them to death. Bad news is, there are also scrolls for Otto.
The game also basically is a fighter/monk/barb gear pinata fest while casters get like 2-3 robes and a single legendary staff, and druids get no legendary weapon and no legendary armor, and ONE SINGLE CHEST armor that works with wildshape and a helm that gives an extra wildshape charge while no other armor and item effects work with druid. Ranger gets a couple of nice bows but zero armorand accessories that boost the animal companion.
Baldur's helm and especially the greatsword are super busted. Lazael is doing 50+ damage per melee swing with the Balduran greatsword bonus, and she gets 3 attacks plus action surge. Add a speed potion and that's like 6 attacks for 50 damage or 300 damage in one round without being reliant on spell slots.
The game was also praised by Fextralife and other reviewers for itemization claiming racial gear bonuses. What they mean is like 95% githyanki exclusive gear bonuses and like one or two drow bonuses, gnomes and halflings get some gloves that boost stealing/dexterity in Act 3, while none of the other races get anything.