I tried VarAC yet again, on the newer Win10 laptop, and made some tests. I have to say there were so few stations to be heard that I simply gave up after a few calls - and that was two evenings in a row on several bands. One noticeable “feature” of the program (VARA or VarAC? I don’t know) is that it somehow takes control of the computer’s sound system while running (probably normal) but doesn’t release them after the program is closed (not good). So, running another digital modes program after closing down VarAC results in the program running fine, but zero sound being transferred to the TRX, regardless of what one does to play with soundcard levels, etc., and hence zero power being transmitted.
Restarting the computer frees those resources up. Maybe it’s just doddery old me, but it’s one hassle too many for me - both VARA and VarAC have now been uninstalled/deleted from this machine, and will not be reinstalled.