McVay is probably not going to run very much 4 WRs. Likely it'll be 2 and 3, and we know already who the 3 are.
It has never made sense to me that the Rams would use a Deep Threat only WR all that much. So that's why I suspected they'd look at a fairly cheap FA, but he'll only be stop gap. You just can't pay big bucks for a guy with limited snaps. I absolutely expect to draft a deep threat WR/PR from the draft and probably no later than the 4th round.
With fewer snaps and playing a deep threat guy, he might give them more games than he's played in the last couple of years. But, I imagine that eventuality will reflect itself in his contract structure.