Not specifically on point as to the plates, since they were not available when I did my setup, but, as to HDMI over Cat5e (in my case), I have had generally good results. I have a Vizio 55" over the fireplace in our living room, and, due to a new grandchild, we did not want to have a lot of components and cables easily accessible to "inquiring minds." My original setup had all my components in a media closet which is located under the stairs, behind the living room wall. I ran a 100' HDMI cable up thru the internal walls, including the second story, into the attic, then down the wall behind the eventual television mount. The long HDMI cable worked for a couple of years, but when the Vizio went bad, it also seemed to give up the ghost. So, while waiting for the replacement unit, I ran two Cat 5e cables behind the baseboards and door casing, from the media cabinet to the television set. It cut the distance significantly, and the result has been very satisfactory. I didn't need the wall plates, since my departure point and arrival point for the Cat 5e was out of sight, so no aesthetics were under consideration.
I ran two lines of Cat 5e, since the Monoprice HDMI over Cat 5e sending/receiving unit required two lines. I now am using two single line sets, by KanexPro, from Cyberguys, which works just fine. I still use both Cat 5e lines, one for the line from my DISH receiver to the Vizio, the other for the HDMI output from my Sony home entertainment center unit to carry the DVD, and other components' signals to the Vizio.
In one of the other forums here, there was some discussion about the need for shielding the cables. Those were centered on the issue of proximity to electric units. In my case, I am not subject to that potential interference.
Bottom line, IMHO, the Cat 5e is a good solution to getting the HDMI signal to a distant point, while staying out of sight. I have always had good results with Monoprice items, the graphic for the plate looks great, and I would imagine the workmanship will allow a clean transfer of signal.
Good luck with your project.