Im looking to speedrun super metroid but I only have snes classic, so I'm asking if it is ok and viable to play on the snes classic (by viable I mean no timing and no loading differences between snes and snes classic

Yes, SNES Classic is allowed on the boards, there are several runners who use it. You can select SNES Classic Mini on the leaderboard filters to see those runs listed, and you can select it as the platform you submit your run for.

For timing differences, Dotsarecool did a comparison for Super Mario World which you can see here: https://www.speedrun.com/smw/thread/8w7yc

There may be differences in loading or lag times for Super Metroid, but I don't think anyone's investigated that. From framerate alone you're only losing about 5 seconds per hour of gameplay.