XR with passthrough+ multiplayer + desktop

Greetings UE community,

I am working on a multiplayer project which should have both desktop and XR (with passthrough) functionality. I have a physical space where I want the xr to be used (there are physical props and so on), but the players also can use desktops to play the game on the web. I want them to be able to see each other’s avatars, and see whatever changes they bring to the world (the idea is that AI butterflies and other critters follow the players).

The general question is: what is the best way/tutorials/any tips I can use to build this?

Some specific questions:
I plan to use Meta Quest Pro for XR. Is there a georeferencing/object tracking feature (like in AR) I can use to make sure that my level is set is anchored in place exactly how I want it (relative to the props, which are not movable)?

Can I build cross-platform AND multiplayer? (I worked in singe player only before, so this is a new territory). There won’t be any interactions between the players except them seeing each other’s avatars. ( I may introduce an AI that would be a de-facto interaction between them though).

Please let me know if there are some obvious problems with my approach which I am failing to see now. Any tips are very much appreciated!!

it’s possible to have cross platform and multiplayer with quest + windows desktop pc - making it work for mac + quest can be a bit more complex as the functions from the quest plugin doesn’t compile on the mac.

For locating your vr coordinate space to the world, you can look into spatial anchors or shared spatial anchors.