With regards to "Small-sized characters and characters who are standing still can hide more easily." GM p82
Size bonuses are based on appearance.2da and not the feat, so the effect can be determined between a small character and a larger character with the same skill. Small size does give a bonus to your combined modal stealth Difficulty Check; however this doesn't show as a skill bonus but is a stealth check modifier, like standing still.
NWN listed relative size modifiers (Tiny: +8, Small: +4, Medium: 0, Large: -4, Huge: -8) effecting both move silent and hide DC (likely due to one DC roll for a combined check) however modifiers can be conditional; like you're not always standing still and not always smaller than your opponent.
Knockdown and Disarm also suggest relative size modifiers and +4 per size difference, this might be the same for stealth. However the AB and AC size bonus are not relative, even though implied "when dealing with larger creatures." or perhaps the small +1 AB negates the small opponents +1 AC anyway.
The related racial skill affinity feats are working, as they are skill bonuses on the character sheet. Ragimund (talk) 10:51, March 11, 2020 (UTC)
If, based on your observations, you've found all this to be true (or at least, very likely to be), please incorporate these changes and make adjustment as neccessary on the main page Raelind (talk) 22:56, March 13, 2020 (UTC) Do you know if the size modifiers are relative as suggested? AB and AC aren't. Isn't that part of the purpose of the talk page? get confirmation or consensus Ragimund (talk) 01:47, March 15, 2020 (UTC)
Seems relative size "in effect". A small character hiding from another small opponent still has better odds than a medium size hiding from the same small opponent. Probably not +4 per size as KD and Disarm but like AB and AC a fixed value, as the table provided. I suspect a Dragon will still have trouble sneaking up on a Halfling.
Minor problem, the nwn2db.com lists on the summary sheet a small stature hide skill bonus of +4. It's not that you don't benefit, it's more a DC modifier. So it effects both skills but doesn't show on the character sheet. (Both skills was mentioned on NWN) Ragimund (talk) 10:49, March 20, 2020 (UTC)