At the moment the dividing line is the middle of the Tay Bridge. In theory the likes of Montrose would be relegated to the HL which is causing loads of discussion in non-League circles. In fact Brora came very close to replacing them 4 years ago.
If Cove beat Berwick the LL will simply adjust to accommodate Berwick and stay at 16 clubs, as it has the EOSL below it. In any case it looks as if Whitehill Welfare will be relegated and replaced by EOSL Champions Bonnyrigg Rose, subject to them gaining a license.
The SHFL can easily run with 17 - they've had 15 recently. Their stated objective is to run with up to 19 after which they would split into 2 divisions of 10. While the pyramid is developing apace in the south, nobody really knows what is happening in the north, as apparently the HL is open to applications from new clubs but this is hardly ever tested. The preferred SFA position is a HL of 16, i.e. 30 games. While there are probably not enough clubs in the north of Scotland to sustain a proper pyramid structure, it means that the lower regions of the HL are effectively just an old boys' club for the likes of Fort and Lossie to survive.