Hey welcome to the group, As far as the sabers sinking/floating the do both some will float some sink. One way to check is with a black light (UV light) I have found when you place them under it they glow kinda like a lightstick. also you can see how wasy they bend the repos are harder the vintage ones, and see if there is any lettering. Flashing around the edges is also a good sign of fakes.
You can find more info here that will be very useful as well,