Hi
No one has responded to you query so I will give it a go.
I don't work for HP.
Another forum member may have experience working with this chassis and can give you a better answer.
I would think you could swap in a liquid cooling system if your PC had a liquid cooling option at purchase.
You could probably find the HP liquid cooling components that are compatible with your PC using HP Part Surfer.
Looking at a pic of your PC's chassis suggest it would be highly unlikely you could install top case fans.
The top chassis has a carrying handle and appears to be solid surface from the carrying handle to the back of the case.. You would be in a better position to determine if this solid panel is removable. You would have to check inside the chassis for fan mount points and verify you have the proper clearance to install top mounted fans.
Had a lengthy discussion in a different thread about installing retail heatsink or liquid cooling in an Omen 880.
You can check it out at this link if you have time to kill.
Tom