Just get whatever the cleanest truck you can afford is. Bonus for Lexus (and if you can do this with Toyota someone chime in), is that you can put the VIN into Lexus' service website and pull the dealer records. I ended up getting a 100% dealer maintained truck up to 3k miles before I bought it from a used car lot that knew nothing about its maintenance history and was selling it too cheap.
You can. The systems are linked. The email you have registered on Lexus is recognized if you try to register it on Toyota.