Under-seat steering, is as it says, under the seat. To a new recumbent rider USS can feel slightly disconcerting, although this feeling soon disappears with more experience. Transmission Usually standard bicycle components with the addition of variable numbers of rollers or idlers to route the chain around the seat, keep it out the way of the front wheel, etc. Some bikes use front-wheel drive where the chain twists on steering and some use an intermediate drive. Seating There are two things to consider here, the design of the seat and the angle of incline.
European designs tend to favour a solid seat back with lumbar suppport.
These can be very comfortable, provided the seat is a good fit to your body. British designers tend to favour the mesh seat, which is a bit like a lawn chair, but with a bit more tension. USA designs tend to either have padded seats or mesh. The seat angle relative to the bottom bracket may effect the amount of power that you can put into the pedals, a more closed angle may allow the production of more power, but I think the jury is still out on this one. Overlap Overlap is where turning the front wheel interferes with pedalling the bike.