Same as for "live" servers - no penalties, bonuses for halflings, warriors and rogues. Believed to be around 5-10%, but I've never seen an analysis. And applies to level exp only, not AA exp.
Play the Race and class you like. XP will come. Having fun playing what is fun to you trumps any XP bonus. IMO.
I'm afraid not. Penalties were removed in several stages, first hybrid (very early on), then more recently, although still several years ago - I'm thinking around SoD - all remaining penalties were removed. The way it was done left a few quirks, as basically all the penalties still exists, but are balanced out by counter balancing bonuses. So there are some glitches with the exact amount earned from quest rewards. But you won't notice unless you start getting very obsessive about exp amounts. Which I did at one point.
Can you provide any proof? I have an iksar necromancer and a halfling ranger - the bonuses are clear, the halfling always gets more xp from everything - however the difference between my half elf bard and iksar necromancer are nothing, the necro has more AC on character sheet and higher base regen however they get exactly the same experience (talking down to the 10th of a percent) from quest rewards etc.
Well, it looks like you have sufficient proof yourself. A few years ago I did some experiments: exp/hr with the same level, same spots; and comparing individual quest rewards while working through Gloomingdeep. You could do the same to see if there has been a change. e.g. Solo experience ranking at 70 and Leveling Zones for 55. That was more about finding the best zones, though.
I want to say all the remaining exp penalties were removed in the TSS expansion. Also important to note that the exp penalties never effect AA gain.
