The fastest speed and cleanest signal is from the test socket, try connecting into that first and then look at your stats using mognuts nifty utility found
here. This will give the max speed possible from your line, fitting another faceplate will not make any difference to the master socket speed but can have a big impact for extensions since you have to run the extension wire from the faceplate. For more details have a look
here.
Welcome to the site, you'll find some very knowledgable people here (I'm not one of them BTW).