I finally moved all of FS2020 over to my HDD (the packages folder) and it makes no noticeable difference on loading times, go figure. (I needed space for FH5 which runs really poorly from HDD).
FS2020 still takes about 3 minutes to load to the main menu and another one or two minutes to start a flight depending on the server. During flight it hardly touches the HDD, so pretty pointless to ‘waste’ 180GB of prime NVME real estate on FS2020.
However I don’t have any add-ons (on FBW A32NX) so mileage may vary with a large community folder.