Toni Wilen

Probable reason is Windows "Fullscreen optimizations". Direct3D9 is not affected by it but D3D11/12 is. It can be disabled by right clicking application, select Properties, Compatibility tab, tick "Disable fullscreen...

Yes but it depends. Anything under pcem-directory won't be accepted. And no "gcc-isms" either.

No chipset model merges superhires pixels (but see below), HRM page 301 only describes ECS Denise "color scrambling" in shres mode, ECS Denise uses a trick to get two shres...