Thowing myself in the deep end (OpenVR, VRUI, Unity)

Hi I'm getting lost in a lot of the terminology in vr development. I am currently using a rig asset called BNG that uses VRUI in Unity. Some assets that I'm trying to use, work with OpenVR and I am not sure if I should switch to a different asset for my rig  and event systems. Which build settings do i need to include when trying to make a solid cross platform VR & AR application?

I am also getting these terms mixed open with openxr, openvr, xr, etc. Could someone fill me in on the latest tools for developing cross platform VR in Unity? What do I need to know?

Sorry, if this is confusing. I'm a little stuck in the weeds.

TLDR: If I am trying to make a good cross platform VR experience in Unity. What type of set-up is going to be the best?