Wayfire's developer here, have you looked into output configuration on our wiki?
Also, is there a chance your 4K screen has negative coordinates? It is well known that Xwayland does not react if an output has negative coordinates (or at least partly negative coordinates).
Also, is there a chance your 4K screen has negative coordinates? It is well known that Xwayland does not react if an output has negative coordinates (or at least partly negative coordinates).