Travelling to and from LAS shortly on Delta. Will have Carryon's only. Looking at maps, it appears we could use either Terminal 1 (Security Check D) or Terminal 3 (Security E). We'll be arriving around 11am and getting back to the airport for departure around 8:30am. A couple of basic questions to which I've not been able to find answers by searching this forum...

1. Is it any quicker/less crowded to use Terminal 3 over Terminal 1 and going to/from Car Rental Center via the shuttle?
2. Coming home, we will likely have preCheck. MyTSA app always shows that Security Check E at Terminal 3 as open, but at different times Security Check D at Terminal 1 is not (though C always seems to be and from what I have read, I'm pretty sure we could use C if we had to and still get to the D gates). My wife wears a medical device that does not play nice with Xrays, so the metal detectors at preCheck are the key to her not having to have a patdown. Is the MyTSA app accurate in this regard (never used it before)? Can we go through security in Terminal 3 with a Delta boarding pass? Assuming there are open preCheck lines in both terminals, would you choose Terminal 1 or Terminal 3 when leaving LAS? One thought I had is that as the "international terminal", a sizable percentage of passengers would qualify for pre-check and the Pre-Check line in Terminal 3 might be shorter?

Thanks for any suggestions.