I only have super Mario 3d all-stars so I was thinking that would be ok for stage RTA?

That has its own leaderboard here: https://www.speedrun.com/sm3das

I'm pretty sure 3DAS is just a category extension with only a full game leaderboard. You could get the nso expansion pack. But you really want an actual n64 or an emulated version. 3das and the switch virtual console version have some input lag or so I'm told