The vast majority, if not all, of the commercially available velomobiles use struts. In terms of where the state of the art is, commercially, its one of these:
https://www.youtube.com/watch?v=aWds-GTFJeoI think he said 60Kmh on 160w. Uk street legal electric assist is 250w. I forget how fast he's been down hill in one. He's got a LOT on his channel. I chose this video as its THE one to have (for speed) and the orange four wheeler is the best of the tourers. Also as its filmed just up the road from here. When I first got the Aurelia I took photos for Viva parked on the grass with that church in the background.
The pukka racers that have had a lifetime lavished on them will be half that weight and so lean they only fit the builder.
The 24hr racers cream round at 45kmh to 55kmh and are build a bit heavier, and very few have any paint left by the end. This particular one has some stats to watch - 750W peak from that rider. The gradient is interesting as even with the slightest down hill it needs no effort to hold speed.
https://www.youtube.com/watch?v=DZUCwnWUxLw&fbclid=IwAR0FeFsr-gB3uAX5HK4AvLOg2RlC00ekHi2VK9rVlEwVArLR3Vhh4KWPPzAWhen I was a kid these (or similar but four seats) were the future of transport, instead its all SUVs.
