The timing for frcing the 2D depends on how you do it. If its set to one button, tap the FRC button immediately after the 2D. If you use 3 buttons to FRC(Like me) then it may be a bit more difficult. Depending on how you do it, if you use for rush downs(Like me) then its most easy to do after 5S,far or close.
My uses for tension varies.
1.Random RC combo/Saving my ass from being open after moves when blocked, and DAA
2.Random ball of doom.
3.FB Puffball in wall combos.
4.FB charge for special kicks.
5.236P FRC, and for JI game,helps with rushdown,and Dash cross-up.
6.236236HS FRC for good fucking damage.
Thats what I use my tension for:keke: . Anywayz, yeah, they won't all work the same way, as each must be altered for different characters,and the person you'r playing's style.