Z axis - Linear bearing or V-wheel?
Okay, I still like Linear guides slightly better.
They are easy, cons, they are expensive. ~$22+ on Amazon for 300mm (250mmZ travel), goes up a few dollars per 50mm. Lets just say $70 for the Z rails. Honestly, I just trust them more and have never used V-wheels in any real capacity, and it means a slightly more simple BOM.
V wheels are cheaper, but take more effort to tension well. We can get a few wheels and print the rest for about $25 for the 3 Z rails, or something like this is ~$32 for three Z rails. You also need to be sure to get V-wheel Extrusions (not a big deal). This seems like the best choice as it saves ~$38.
Looking at those v-wheel plates, I kinda don’t see a reason we could not have both. I think if I designed a part for linear rails, it would take three steps in cad to cut it off and add screw holes for the Vwheel plate.
For the rest of the Z, I know you want the steppers off the Z plate mounts, Steppers up top for easier wiring, and want an optional lead screw mount.