Ideally the lead screw should pass through the center of gravity which again should coincide with the center of cutting forces. Try to get as close to this as you can within budget and other constraints. Having the lead screw underneath could easily be as bad as on one side if that brings it as far from the mentioned position. You might just swap unwanted horizontal forces with vertical. For a gantry two screws is the universal remedy. But it costs money and other headaches.
But the one you referred to does not even try to compensate for having only one screw! It should have 2 bearings on the rail on each side, preferrably with some distance between them. And then a fairly stiff frame keeping them rigidly connected. Then even with one screw it will withstand the twisting forces much better. In all probability good enough for your wood router.
So I would go for one screw, longer rails and closer to a square pattern of 4 bearings.
Vertically it looks OK, as there is not a high "tower bridge". It's easier to add lateral stiffness in the non-moving frame than the moving gantry. Both because you don't add to the moving mass, and because it will not restrict the sideways (Y) spindle/tool movement.
That's my opinion, but I think there are now 6000 members on this forum, so you still have 5999 opinions to go.