Or do you need to do some fiddling to get them to work? if so, what?

RT2 works perfectly in Win10 Pro 1909 as far as I can tell.

I don't own RT3. Several people have said in the past that it did work, but the posts are a bit old.

Apparently you need to disable hardware T&L for Vista and newer Windows, but that is more related to hardware than to Windows itself. Maybe it works as is with Win10, maybe GOG included the configuration by default, or maybe you would have to do it yourself. You'd have to wait for someone who owns it and plays in Win10 to tell for sure.

http://hawkdawg.com/forums/viewtopic.php?f=5&t=2131
http://hawkdawg.com/txt/rt3/Vista_Fix_RT3.txt

On a second look, it seems like it's a binary file, not text, so if you end up needing it you will be better off downloading it directly:
http://hawkdawg.com/rrt/rrt3/Xtras/
(under the "Vista/Win 7/Win 8 Fix" header)

Thanks.