Your texture layout seems fine.
If you really want you can save yourself a channel if you encode normals with 2 colors instead of 3 (by not supplying z, which is directed at the camera anyways).
AO is an option, many PBR renderers omit that because it’s not really physically based any more if it’s prebaked.
For some further reference and maybe Monogame implementation stuff you can check the modelviewer:
Sorry about the vertex texture fetching, I have only ever tried on DirectX.