i'm a little confused and i don't really want to read this whole thread again, i thought earlier you said that your wireless tablets/phones were working ok, but now they are getting drop outs? and so too is your machine used for zwift? what is common here...the wireless router. borrow another wireless router and try that.
you also indicate that going ethernet directly zwift works fine. also points to the wireless router since the tablets have this problem as well.
had to look up the power adapter thing, i would be surprised if that helped at all, more than likely i owuld expect it to help cause more problems than fix any. house hold wiring was not designed with high speed communications in mind. you have no idea what those wires are next to and none are twisted, they might owrk to a certain degree but i would not put much faith in them.
all of your other devices appear to work more than likely because they use TCP and not UDP. and having larger packets is more efficient than smaller ones.