on linux I had a good image viewer that could run a slide show in multiple instances simultaneously but on windows I can't find anything that doesn't force your image viewer into full screen.
Irfanview is a great photo viewer. It will show individual photos, it has a full-screen display or part screen with menus and toolbars. It has 'next' and 'previous' photo commands in both modes. It can do slide shows.
It works fine on Windows 10.