Yeah combos need 2nd pass. Now about this particular combo. I'm not a fan of it for 2 reasons:
1) Execution is really tight. If you are 100% sure you can do it sure go for it. This is probably most possible damage you can get from this situation.
2) If you drop this combo you open yourself for big damage punish
You are correct though. You can easily improve this combo by doing anything else like 1[K] LT > wrB+K > TAS B > TAS B for 86 damage. Less danger if you drop it and almost same reward. This is what I've added instead.
1. What is the difference between notation "!w" and "w!"? It says in the 1st page that "!W" is a first wall hit of combo. is "W!" something different?
No difference just typing error I'll fix this. Thanks
2. How do you execute that super fast AS B when Sophie is glowing blue for the attack time? Do I need to buffer it somehow or meet special conditions?
You need to do it as game says "fast" and you must press B at the same time as 6. Also it's easier to do this from crouch so practice that first.:
3. Are you maybe aware of frame window length for followup 4 or B in AS/TAS B:4_B?
Muscle memory more or less. In training mode at the moment you see "MID" you should press 4 or B. Timing of 4 or B depends how far away you are from the opponent and if you did normal or "fast" version of AS B. With that in mind you can only get 4 or B follow up if:
a) You're at right range. If your blade won't slide into your opponent you can't get follow up (if you hit with tip Sophitia won't say "Pardon Me")
b) You must hit enemy from a front. You won't get follow up if you hit your opponent directly from left, right or back.
c) Enemy must have STUN. You don't have to worry about this unless you do wall combo. In wall combo at certain moment AS B loses it's STUN property.
Here you have video showing everything I talked about:
Thanks for feedback!