I had to create a few 250 Gb TDevs for a host and I created them as 5x50 Gb Meta because I was under the impression that the 2,4,8,16 rule for creating applies only to thick devices and doesnt matter when we are using Thin Pools. Is this correct? Or would I rather have them created as 4x75 Gb Meta. Would there be any difference in performance of the two?
You are correct. For thick devices, powers of 2 fit nicely into the backend layout. Since the TDEVs have no direct relationship to how the TDATs are placed, this is no longer a consideration.
For the thin meta, the extents in the Thin Pool which your thin meta bond to are distributed across all the data devices. You don't need to follow the 2,4,8,16 rule.
Since VP metas have nothing to do with the backend layout at all, there is no such need. However there is nothing wrong with sticking with powers of 2, since they would also work fine.