650mb would theoretically be better due to wider grooves and/or no overburn area where the laser might get stuck, but I've been using 720mb (maybe only 700mb?) JVC branded Taiyo Yuden discs for years without issue. I'd not worry about it.
CDRs are only going to hurt your drive if you ignore that it's not working correctly. If it plays without issue, your drive will be fine; if it struggles and loses its place and has to refocus often, you'll kill it eventually.
1.0 syscard is pretty uncommon, but most any 'regular' CD should work just fine. The more common 2.0 card is mainly big fixes and an added music CD player. You definitely will need a 3.0 syscard eventually, though, as there's way too many great Super CDs that need to be played; including those NES2PCE games, I believe. I'm fairly certain that the newer everdrives can be used as a 3.0 syscard, so I'd invest in that before bothering with a real one.
I use Imgburn and haven't made a coaster in years. They always fail validation, though, but they still work fine.
Just my zwei pfennig. Welcome aboard, best of luck to you on your burning adventures, and please keep us updated on what did (or didn't) work for you.