@jenkinsm
I am keeping roughly the same distance from objects/walls when I am taking photos.
So if some object on my photo has 394 pixels height and real height 460mm, then I know that pixel density of my photo is ~ 0.856pixels/mm.
If software you use doesn't tell you what is the texel density of unwrapped object, you need to calculate it:
Be sure, that all unwrapped UV islands has normalized size and are not stretched or compressed.
Then choice some polygon island in UV editor and measure its width/height in UV range (0.0 - 1.0). For example groups of polygons of some wall in UV editor has min. 0.452 and max. 0.687 in U direction - so you know the width is 0.687-0.452 = 0.235 and that is 1925 texels if you will be using 8k textures (8192 * 0.235 = 1925). In reality the size of that polygons on wall is e.g. 2400mm - so you know that the texel density of your unwrapped object on 8k texture is ~ 0.802 texels/mm , which is slightly lower than pixel density on photo...so you should make the groups of polygons in UW editor 1.067x larger to make texel density the same as photo pixel density.
For your VR project it would be good to use many smaller textures if you want to achieve maximum performance. Keep all details is sure thing. You should unwrap the whole environment in way, that all surfaces which are close to each other in reality, will be on the same one texture. This is good in terms of how GPU is sampling textures when rendering some part of the image. If some groups of pixels(e.g. square of 50x50 pixels on your screen) is using one texture and that texture(or it's required MIP level) is also small (1k or 2k) is highly likely that GPU will transfer that texture from VRAM to L2 cache and will be sampling it from cache(many times faster) and not from VRAM.
Check what is the size of L2 cache on your GPU you will be using and then choice the right size and compression of textures(1k DXT5 is 1.3MB, 1k DXT1 is 0.7MB, 2k DXT5 5.3MB, 2k DXT1 2.7MB, etc. ...).
There is no simple exact rule, how big textures should be, because the overall performance depends on your screen resolution, camera fov, object distance from camera => required texture MIP level,...but with smaler textures the chances are better.
So try to avoid large textures and when unwrapping the whole object or environment try to avoid that on one texture will be parts of real environment which are far away from each other.
You will need some good unwrapping software (I mentioned RizomUV), you will probably spent some time unwrapping your objects/environment to several UDIMs and then jump back to metashape bake the final textures
.