Does anybody know how 1.17 will affect speedrunning? I feel like it won't change too much, so will it have it's own leaderboards, or will 1.16 now be 1.16+?

It's probably to soon to tell; after all, we know very little about the specifics of 1.17 as of now. The reason that RSG is split into three categories is due to the vastly different strategies used to complete runs in each of the versions (as well as them having a substantial following of users who are interested in running them). So, if 1.17 adds something that is revolutionary to Minecraft speedrunning, then maybe, but if not, then it will probably become part of the 1.16+ subcategory.

Ok. I was thinking about the brush. The ability to unearth blocks and items randomly just adds another level to speedrunning. I think it depends on the crafting materials required for the brush.