I have built a yuloh and I can do 1knot for a few hours, or 1.5 knots top speed. I can go against 10 knots of wind and it slows me by .5 knots. Normally you sail in less wind than that. It is ideal for using with favorable tide and little to no wind.
I think it makes sense to try oars too. It would work different muscles if you get tired of the yuloh. Also the yuloh dimensions are critical to get any decent efficiency where oars I believe are a little more forgiving (use large area oars which are fairly close to the boat) You can probably go faster with oars, and it would be easy to negotiate having two people working them at the same time, but would use more effort than the yuloh and would stick out the the side which might make docking
more of a pain, but no big deal really.
Now, another really good idea you should consider:
Attach bicycle sprockets and chain to prop shaft with chain coming up into cockpit
. Put the largest possible prop you can with 3 or 4 blades. The larger the diameter of the prop, the better. Typically gearing 4:1 to 6:1 (experiment with this) so the prop spins much faster than the pedals. Should allow you to achieve similar speed to rowing or sculling using completely different muscles. If you had a 3ft diameter propeller
with perfect dimensions, you could probably pedal the boat at 3 knots or slightly slower for long duration on a 27ft boat.