Since starting this thread I have had several useful discussions (on and offline) on the subject. I have a query off to Parallels to which they have not yet responded.
To narrow and make my "concerns" more specific, I reframed the question to be whether I could, using Parallels on the M1 (or successor) chip use Windows 10 Pro because I will not run Windows 10 without using Bitlocker. While rephrasing the question this way does not obviate all of the other questions it narrows the focus considerably.
A series of answers has led me to conclude that there is nothing in the available literature to say that Windows 10 Pro could run within Parallels on an M1 chip. There is a goodly amount of literature which says that Windows 10 Pro will not run within Parallels on an M1 chip. No one that I discussed the matter with had any idea whether Bitlocker could run on M1 (or successor) chip within Parallels.
There was a consensus of opinion that if I periodically use Microsoft support on the Windows 10 Pro installation it would be imprudent (at best) to switch to a version of Windows (the ARM version) without support.
Unless that consensus changes between now and when I purchase my replacement for my current (and much appreciated) Imac I will buy a Windows box to replace it. This will be the first time in over two decades that I have purchased a straight Windows box.
