One thing I've been wondering... What do I do when I've got a grab on a spacie, are there any guaranteed combos I have after a grab or...
And it's the same thing with the other high tiers I guess
Low percents probably down throw if they don't tech you can get a downsmash / jab reset usually. Or set up some sort of tech chase. So if the spacie is normally teching you can do a quick bit of dashing around outside of get up attack range after the down throw and react to their tech / roll / get up attack. Techs might be harder to follow up on though.
Mid/High % - Up throw probably you can usually convert it into like nair or sometimes dair to send them off stage and set up an edgeguard I haven't messed around with it too much but you might also be able to do upthrow>up-air>land on platform>Dair or Nair I might try this
Stupid high percents (like IDK 150%+) you can down throw into really silly stuff like forward tilt lol
Against floaties definitely downthrow for days you can convert into downair at high percents and kill.
I don't know as much against shiek / marth