I just know the matchup from chuns side. So I don’t recall the normalo guileis opposed to use.I DO know it is a guessing game though and a few times guiles told me the normals but I never remember for more than a week.
As for the neckbreaker, against average chuns ALWAYS reversal flash kick. The timing for it is really strict and i still mess it up ocassionally. The problem with this is that builds a bad habit when you get a chun who times it right. Your flash kick will whiff. Try to guage where the neckbreaker will make contact. Often I know I messed up the timing right after I push the button. If chun makes contact with you high (its really only safe if she makes contact and her legs are BELOW the stage) then its a free reversal flash kick, assuming you have the timing down. Otherwise don’t risk it you’ll eat the neckbreaker if you time it wrong. She only crosses up guile with her neckbreaker if she’s at point blank. So guess normal more often than not. Other characters its block normal always or its 50/50 something about guiles speed or hitbox makes it so its harder for chun to catch up to him for a crossup neckbreaker than normal (which is why this is the only match up you’ll see me do a ton ambiguous neckbreaker occasionally, simply because even with chuns amazing walk speed, some situations she can’t get close enough). When it looks ambiguous try to guague if she had extra time before pressing kick.if so its a guess. If not block normal. Judge by the actual time she has, not by the movement. I’ve purposely stutter stepped REALLY early so it looks like I ran out of time to trick guiles to blocking normal instead of backwards.
If chun jumps over you before meaty neckbreaker block the original direction. She can’t do it the other direction without making it look really obvious. Else she mistimed it and you can flashkick.
Again, its only guiles that can use these tricks, everyone either blocks normal all the time or its an absolute guess as we can dance around the sweet spot for a crossup.