In fmSR I've got a bunch of fields on the various Table0x layouts that I am not using - mainly date and integer fields.

I'm assuming that I can remove them without issue if I wanted.

Is removing unused stuff a good practice in fmSR or should they be left alone?

I'd leave them alone. That way their object names are still there on the layout in case you eventually want to search more fields OR use that layout as the basis for a search on a new table.