I believe Chii's version of the strategy guide would answer your questions but I'll just tell you a few things.
1) Arc is very hard to win with consistently, not out of single wins. She requires alot of patience against most of the cast and alot of skill. She's overall an interesting character and is very simple in theory, just takes some knowledge beyond your character (which means you) to win.
2) Arc doesn't have many bullshit mixups and oki, but her rush/frame trap game is where she's the strongest. The corner is where she is the strongest and the most feared. Most of your midscreen combos will lead them to the corner anyway (if you know your 4b relaunch combos) and will be much easier to make your rush game count.
3) 5b (charged) and half charged 5b mixup is probably one of the best mixups she has. Since 5b (charged) is overhead, half charged makes it look like its coming, but it really isn't. Cancel this with 5a to make it a high/low mixup (mixing up between the 2a and the actual overhead)
I do have some more info but I'ma have to go through it some more. plz make your way to #meltyblood-active on irc.rizon.net. Lots of people like yourself are there and if you have caster, you can play matches against people and they will be pleased to help you.