@rlkeeney @jonas thanks lads, sorry, only just saw these replies.
Ok so for MP3 ID3v2.4 I shouldn't need to do anything given I have those 4 options ticked, i.e.:
Once a track has finished playing in Strawberry
-- if I've rated it in Strawberry, Strawberry should save the rating to the file
-- Strawberry should increment the playcount +1 and save that to the file
If I edit a track externally (for reference, I would only be saving other tag fields, never rating nor playcount) Strawberry will re-read the track... so if I listen to a track in Strawberry, rate it, the track ends and the rating and playcount are updated by Strawberry to the track's ID3, then I change the track's comment externally, Strawberry should subsequently re-read the track's info (when it does a full scan?) and see the updated comment, and the rating & playcount should still be correct?
I might need to do some testing on that last one. For some reason it seems I have LOADS of tracks I've definitely played countless times, which have playcount=0, and similarly loads I've played and rated which have blanks for both. In the meantime I've edited various ID3 details for those tracks, but as I understand it, that should never compromise the playcounts and ratings, so it seems something is behaving incorrectly...