1) The cap is the same basically 500 crit for 50% but you'll need more because crit strike resist reduces it. For PvP you're looking over 950 crit strike is a good number, that depends on the average crit strike resist of other players (over 450~ resist). PvE you'll want between 1000 and 1100, depends on the instance but 1100 you'll be good for everything I think.
2) Maximum stats what do you mean exactly ? The stats you need for each or how much can you reach ? There is no limit basically because most stats in aion have caps but that gets reduced by another stat so you need to have more to counter it. So I can't tell you how much exactly can you reach cause it all depends on your opponent and you just need to basically reach optimized numbers at end game.
- Block cap is 50% so its 500 but you need to add it to your opponent accuracy. Generally average players accuracy late game is 3000 so you need 3500 block to have 50% chance of blocking. But the more precision they have the less chances you'll get (example your set is at 3500 block but a player have 3200 accuracy => you will get 30% chance).
*So for player socketing accuracy you will need more, take 3500 as a starting number to work for the average player.
**Parry is capped at 40% so 400 and evade at 30% so 300 as a bonus info.
- MR not sure if in this patch is also 50%, someone can correct me if I'm wrong. But in any case it's the same concept, if a player have 2300 MA (which I think is maybe the max they can reach overall with socketing composites without sacrificing too much MB) you'll need 2800 MR. On average players I think they will maybe have 2100 MA so start by reaching 2600 MR I guess. *A lot of skills have their own bonuses and penalties of MA that also goes into account.
- MS is another story as it reduces your opponent MB at a 1:1 ratio, so you'll need to know how much MB they can reach but you won't be able to go even with it to like reduce it to 0 lol. Keep in mind MB cap is 2900, any MB over it doesn't add damage it's only purpose is to counter the MS of targets, so you just need the best gear for an MS set and get as much as you can to reduce their magic damage. (I think ancient coin leather is best for this with a shield that have a lot of ancient manastone slots like rune shield tower)
- Attack has no cap so put as much as you can on your DPS set after you get the caps on accuracy and crit which are the priority (attack will not matter if you can't hit your target and getting close as possible to 50% crit is crucial).
-Crit see (1).
- Accuracy I basically explained it with block.
=> So in short for PvP, for a DPS set you are looking at reaching 3000+ accuracy with 950+ crit and as much attack as you can fit. Block set start with 3500 block, you can fit in crit with composites to also be cap for crit for a bit of damage but at the expense of less block. MR is same with block but try to get 2600+ to 2800. You can try finding gear calculators online to try and plan a bit and see the numbers you can reach. If I did a mistake on some numbers someone please correct me.