Hi!
Keep in mind that this is more an action PW rather than a RP one where PVP can exists. But here we go with the answers.
The AB and the saves are scaled the same way, if on normal progression from 20 to 40 you get +1 to AB and saves every 2 levels, the scaling has been done so from 41 to 60 you get +1 every 3 levels and from 61 to 80 you get +1 every 4 levels.
To say it with numbers. If from 21 to 40 a character gain +10 base attack bonus from 41 to 80 a character gains an additional +12 so is not that much.
Ability scores, feats and skills gain I'm pretty sure is hardcoded. So you still get a feat every 3 levels and an ability point every 4 levels. Then you get bonus feat if your class allow it. The ability cap is up to +20 instead of the +12.
The AB is scalling only to an additional +12 (plus all the feats that you can get in those extra levels) so is not that much. A +20 AC on every item will give you an un-hittable character probably.
Casters now in NWN stop progressing past level 25. This is a shame. I would like to scale duration and damage of every spell to LVL 40 so you can have pretty powerful casters and not what they are now. But is a massive amount to modify so if there is no script pack available yet it will be a progressive modification to make casters useful.
Ok, so here is the thing. We will have standard NWN shops and then all the random generated items:
So you kill an enemy. A rat won't drop an item but a goblin will probably do. Chances vary from 8% to a 15% to drop a specified item. Rolls are done separately, so for every possible type of item (armor, weapon, shield, misc item (here I include clothing and helmets), scrolls ...) a roll is done and is compared. For example, only monster that cast spells will drop rod, wands or scrolls.
Now, we see the number of properties the item might have. It can go from 0 to 8 properties:
Inferior 02% 0 properties
Superior 25% 1 property
Enchanted 20% 2 properties
Powerful 15% 3 properties
Champion's 13% 4 properties
Epic 10% 5 properties
Heroic 07% 6 properties
Legendary 05% 7 properties
Titan's 03% 8 properties
And then, the quality of the properties are defined by the level of the mob. A BOSS mob will have more chances to drop good stuff and will go from 3 properties to 8.
Then, the bonus, the attack, enhancement and AC bonus is up to +16 on level 75+ mobs. Then, the bonus can be a normal bonus or against an alignment group (good, evil, neutral ...) or against a racial type. If is not a general one, the bonus is increased in 2d4. Meaning you can get a +20 bonus against a special racial type or alignment.
Armors and shields will always have an AC bonus property if they have at least one. Same with weapons, will have an enhancement bonus if they have at least one. Then if the weapon enhancement bonus is against a racial group, the damage bonus will also be targeted to that racial group.
The Runemaster is able to create items up to +20 but that will take time as they need to find all the needed runes and items with sockets. So that is an advantage for the pseudo class runemaster. Each pseudo class or subclass or profession has its own advantages.
About immunity on items. They will have a maximum of 1 immunity.
If you have any questions feel free to ask. But also give all the suggestions you want '>