I like to go completely round underfoot, so an angle grinder is really the only practical method to achieve this besides a big ol file. I dont think it matters too much what kind of wheel you have on, but you do have to be careful and make lots of really light passes. I also leave the tips and tails sharp, and it's always worked great for me.
You don't have to take the edge off for rails, but if you are going to be hitting them a lot, I think it's advantageous to go completely round in the interest of longer life out of your skis. A round edge should be much less prone to cracking than a square one because of the larger area the pressure is distributed.