I have been having problems with Mac v.2018 which I will document here shortly.
In the mean time am I correct in thinking that if I revert to v.2016 I can still use the
newer RealTracks and RealDrums that came along with the 2018 release?
Indeed we need more information from you as to the actual problems you have with Mac 2018 Band.
You bring up a very interesting idea that I am not so sure will work.
As best as I understand this RealTracks and RealDrums are very closely related to the style when you launch Style Picker.
Therefor using tracks and drums created by another version of the Band can't be loaded into the Song you will be working on.
If this is wrong, someone who knows more than me about the Mac Band will be along shortly to correct this.