BBC are reporting that:

League 2 will relegate 1 team (due to the demise of Bury trickling down).  That would currently be Stevenage, but there is a FA disciplinary hearing today which might deduct points from Macclesfield Town (due to non payment of wages - again) and send them down

National League have met and put out a proposal to be voted on Monday) which will decide the three leagues on a Points Per Game basis

Barrow would be promoted to League 2 as Champions, with Play Offs to decide the second team.  Brendon Kiernan's side (Harrogate Town) are currently second and could go up.

Only one team will be relegated from the National League, which would be Chorley to National League North

Only one team would be promoted from the National League North and National League South.  Based on Points Per game that would be Kings Lynn (who go above York City) and Wealdstone.

No teams will be relegated from National League North and National League South.

If you have followed all that, it will probably mean we will have 21 teams in National League South next season (if it ever starts).  There is however a possible "sting in the tail" - it is feasible that Macclesfield Town will be forced to drop two leagues (similar to what happened to Boston United some years ago), in which case it would be the National League who are one short and we would see one club transfer from National League North to National League South, probably Gloucester City or possibly Brackley Town.