Currently I am trying to make some detailed documentation. Does PRC team has any tool for making anything like it? I suppose the PRC online manual was built by some script. Additionally point me to any tool or site that could help with this task, thanks.

The "Manual Generator" for PRC Pack is located in SVN repository:
https://svn.code.sf.net/p/daprc/code/nwn/DocGen/
It requires copying some files from the source (icons, tlk etc) but I'm sure you'll figure this out.

I suppose you could edit classes.2da, but you would also have to edit dialog.tlk (you need special tool to do this) - I don't know if there is any way to load custom tlk before loading a module. In my opinion this is not worth the hassle.

From my understanding this allows you to learn new spells with prc classes without using the clunky menus you had to use before this?

Yes, although I noticed some bugs ('Bad strref' instead of name for some spells and spells with subradial options do not work correctly). I am not sure if I have the latest version of nwncx_patch.dll though.

Also, custom classes at start without using the char creator? Does this apply to races too?

Again, Yes. You can select custom races by typing the name in subrace field.

The code responsible for this is located in spellhook (as you can see potions and 'on hit cast spell' are not restricted). I am no PnP expert. That's how it has been coded. If there are rules in PnP saying that magical items can be used without verbal or somatic component I will change that.
       if(GetIsObjectValid(oSpellCastItem))
        {
            // Potion drinking is not restricted
            if(GetBaseItemType(oSpellCastItem) == BASE_ITEM_ENCHANTED_POTION
            || GetBaseItemType(oSpellCastItem) == BASE_ITEM_POTIONS)
                return TRUE;

            //OnHit properties on equipped items not restricted
            int nSlot;
            for(nSlot = 0; nSlot<NUM_INVENTORY_SLOTS; nSlot++)
            {
                if(GetItemInSlot(nSlot, oCaster) == oSpellCastItem)
                    return TRUE;
            }
        }

I think I've tried some time ago changing Acolyte of the Skin to give him full caster progression, and back then I just put a "1" instead of a "2" in classes.2da in its place... I believe it worked, but I cannot say for sure.

This would only affect spells per day for original NWN classes (wizard, cleric, druid etc) - no caster level increase though. New caster classes added by PRC require some more scripting.

Xwarren, could you tell me where are the prerequsites for Epic Eldritch Blast? When I gave epic progressions to eldritch disciple and theurge they were not able to take epic eldritch blast despite having invoker level higher than 20 - I also couldnt do it with warlock 16/something 4 with practiced invoker, which leads me to believe it is coded to require 20 levels of warlock instead of 9d6 eldritch blast, which requires invoker level 20, unless you are also an enlightened spirit (continues eldritch blast but does not increase invoker level), which is not added to PRC.

I just checked cls_feat*.2da for eldritch disciple and eldritch theurge - there are epic feats in there. I remember that I was working on epic progression for these classes (I am using files from SVN). I will test if it is working.

Edit: I have tested this a with a following character: Warlock 6/Dread Necromancer 4/Eldritch Theurge 10+
- epic Eldritch Theurge progression is enabled - I didn't have to change anything to get 11th level
- You can select Epic Eldritch Blast feats on Eldrith Theurge levels
- The scripts will make sure that you have at least 9d6 blast damage - I couldn't take this as my first epic feat because of that (so I took Practiced Invoker instead) - after that I could select this feat on following levels (with only 6 levels of Warlock).
- a function i prc_enforce_feat.nss checks for blast damage:
    if(GetHasFeat(FEAT_EPIC_ELDRITCH_BLAST_I))
    {
        int nInvLvl = GetInvokerLevel(OBJECT_SELF, CLASS_TYPE_WARLOCK);
        int nEldBlast;
        if(nInvLvl < 13)
            nEldBlast = (nInvLvl + 1) / 2;
        else if(nInvLvl < 20)
            nEldBlast = (nInvLvl + 7) / 3;
        else
            nEldBlast = 9 + (nInvLvl - 20) / 2;

        if(nEldBlast < 9)
        {
            FloatingTextStringOnCreature("You must have 9d6 eldritch blast to take Epic Eldritch Blast.", OBJECT_SELF, FALSE);
            return TRUE;
        }
    }

I should probably mention that you'll need to compile 'prc_levelup.nss', 'prc_onenter.nss' and 'prc_onleveldown.nss' for it to work :p

(actually all the scripts that use EvalPRCFeats(), but compiling those I mentioned before should do)

Actually there is one more check before adding new invoker levels:

if(GetLocalInt(oCaster, "INV_Caster") == 2)

This is set in prc_inc_function.nss and you have to add information about new classes there as well. No 2da edits are necessary. And yes - putting files in top hak will work.

I have searched for 'CHUNK_SIZE' in PRC source code - only found two occurrences and none of them had 'const' qualifier. Which PRC version are you using?

To compile our scripts it is recommended to use nwnnsscomp.exe. It is a command line tool so if you double click on the exe it will do nothing - you need to pass parameters in command line for it to work. Hope this helps