An explanation as to how SA's work? Sure (If this isn't want you want, I apologize...)
The skill is self-explanatory: the higher the skill, the greater the boost.
The Accuracy is how often it hits. Every action, you have an [Accuracy]% chance to have your SA activate.
TBH, and this is only my opinion, SA's really aren't worth it unless you're willing to invest millions (literally) of FE's into it.
...except one. Escape Submission. Whereas bonus-based SA's are only marginally useful unless you have them jacked up ad infinitum, Escape Submission is percentage-based, so every rank gives you an additional 5% on escape submission, and that does make a difference.
IMO, it's the only SA worth investing in.
But, your build, your call.
(Sorry for the necro; saw nobody responded and wanted to throw my 2 FE's in)