Hope you don't mind the cut and paste.......
"Do you fit a bent similarly to a traditional bike?" No, stand over height is not an issue on recumbents. To fit a bent you need to find your X-Seam measurement. Sit flat on the floor, with your back against a wall legs stretched out, measure from the soles of your feet to the wall. This is your X-seam. Just like uprights you can change handle bars and adjust the stem for a better fit.
"Do they come in size increments?" Yes, most bents are very adjustable. But if you put a tall rider on too small a frame, or the other way around. You may end up with a bike that handles poorly. The front wheel may not carry enough weight or too much. It can really affect the way the bike handles.
"What other concerns are there when picking out a bent?" For the most part most of the builders have sorted out problems with there bikes. Some of the newer builders may still have bugs in there bikes. One thing I try to avoid is special parts that can only be bought from the builder of the bike.
The RANS Velocity Squared and Stratus are fine bikes, you may also want to look at Easy Racer, Vision and Burley.
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." - Arthur Conan Doyle