So I hadn't realised I was not using the latest version of QB64. After updating from v1.2 to v1.3, the IDE seems to be behaving far better with my 4K display. I still need to override Windows DPI scaling, but now I can actually put in custom screen sizing like 80x25 or 100x50 and it works. It also seems I can also use a custom TTF now without it pixelating it from a tiny size.
Thanks a lot for all the work, devs! Much appreciated.