Since last year, there have been a couple of attempts at Vulkan and Direct3D 12 providers, so in one way or another you'll be able to use both of them.

Delphi/FPC headers is not a problem as there's an internal automated tool for that. In fact, PXL comes with its own headers (see PXL.Windows.xxx.pas files) for different Direct3D versions, codecs, etc.