Is it just normal gameplay or are glitches allowed if you stay in the games borders?

Glitch are indeed allowed. Glitches in this game are rare and tend to not be hard or save much which would make it hard to justify a glitchless category but as we are finding more and more glitches which are more and more game breaking things might change in the future. In case you were looking for the glitchless category of this game Inbounds is the place to look as all the out of bounds stuff is very much game breaking.