Open Radeon Settings and go to Display to see if you have a scaling option. If so you should be able to scale down for the game so that it fits the screen.
I don't really know why but every time I update my video drivers I have to adjust the HDMI scaling on my second monitor; probably because I always do clean installs.
You may also want to try disabling Fullscreen Optimization under Compatibility options under Properties for the game.
<edit>As an add-on to the DirectX thought I have installers for ~1800 old Reflexive Arcade games... Way back when I helped them with some JavaScript code and they gave me pretty much everything they had at the time. Reflexive was bought out by Amazon.
Anyway I have SO MANY of their installers that I don't even have a clue as to what all is there to this day. Thinking old games I installed a few and some failed due to a failure to be able to access Direct 3D which, of course, is part of DirectX. Some of the failures I could probably fix with compatibility mode settings but didn't bother.
LOL! I think I'm about to go on a Yahtzee marathon.
Or mayhaps I'll go to my SNES emulator and play some Yoshi's Island.
Sigh, I wish I could find the original public domain version of Bud Redhead. It was/is a very fun platform type game that was totally free.