Living where you do, there is one easy answer to all your questions: you need to visit a gentleman called Kevin, who runs an operation called D-tek. He is essentially a dealer in good quality second hand recumbents of many styles, and I read that he has been very helpful to many. Google around and /or search on here, you’ll soon find him.
The fact that he usually carries a varied stock is also an essential plus for one in your situation, starting from zero. This is because recumbents come in a huge variety of forms and geometries. The only way to find out what will suit you is to plonk yourself down on a few and experiment.
I am into two wheel bents which come in long or short wheelbase, and in various seat heights from super high to super low. There is also a wide range of steering and handlebar configurations. Degree of recline, seat hight and bottom bracket height relative to ground and relative to seat are also big factors for both two and three wheel bents. Get the picture?
Visit Kevin if you can, read up as much as you can (the US site ‘Bentrider Online’ is a very useful resource and not totally US centric.) and finall, look at lots of pictures, generally, and on manufacturers websites. Some names to start with: Ice, Haase, Greenspeed, Azub, Nazca, HP Velotechnic, Linear, Bachetta . . .
Buying something cheap and entry level like a KMX Kart may not be a bad idea. You may end up loving it, or you may end up selling it on with a much clearer idea of what you do or don’t like!
And have fun! Many, like you, investigate bents for medical reasons. That was never the case for me. I love them because they are a blast!
Hope this helps . . .