As an update I have also been in touch with support about this. After trying several things the conclusion is I am wrong - performance is the same on Windows 10 and 11. I have been running benchmarks in various configurations to test, rather than just looking at the performance of one file.
Windows 10 shows no use of the GPU because Hardware-accelerated GPU scheduling is off as suggested above. I had to do a search on how to turn this on and off, but it is on as a default in Windows 11 and off in Windows 10. Turn on in Windows 10 and task manager shows stuff happening.
The 2080/3060 are a lot better performance than the 1660 in all machines. I feel that this used to be better. As an example in the bench mark the 2080 can manage 14 fps, which the 1660 manages 1 fps - a staggering difference when I look at general benchmarks for the two cards performance. I assume Topaz has been optimised to use some of the new technology in the 2080/3060. If I find any way to improve it I will post here for anyone else who comes across this topic.
However, in future I will not even be trying to use the 1660 and instead using 2080 or 3060 for all Topazing.
Thanks for your help.
