to oneEhtie- jibbing definitely affects your edges, but you can get them resharpened, and unless youre boosting pipe like a pro you dont need to worry about duller edges
as for the 270 on... when i first tried them i thought of it as a 360, but thinking of it as a 180 and then doing the last 90 with your feet helps you stay on if its a longer rail or you have a kink to deal with. so when im gapping onto a rail or im planning to 270 out, i think of it like a 360, but if not its key to think of it as a 180