Can I use UE5's Rendering Engine?

of course you can !

blender <—> UE5

modeling in blender and displaying in UE5 is pretty straightforward.
You can also consider U3D as a realtime render. It is what i use for my project

I know very few things about UE5 but for the unity part, all imports are fully scriptable in C#, allowing you to make intelligent import of you models, materials, rigs, animations, etc…

EDIT: if you intend to make still render ( eg 1 picture ) i think cycles will be what you need. UE5 or unity are render engines aiming at realtime rendering.