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No point going with expensive screws and keeping round rails.

Profile / square linear bearings are FAR superior to round rails

Lifting Z is a good stiff design.

But having the X and Y down the bottom is weird.
You have 4 rails on the X axis - this is a lot of added expense, but worse will be the difficulty of aligning 4...

Workpiece mounted on blue rotates? A polar axis.

Currently you have X (yellow, side to side), Z (column up and down), and polar (blue)

Do you plan to do many flat surfaces?
If you want to do...

Delta do have torque graphs. They have a good manual which is partly why they are worth paying for.

You will get 100% torque to rated speed then it will drop off to max speed.

You then have...

For a wood router 15mm profile rails are more than enough load wise.

Bigger rails are sometimes easier for a couple of reasons:
Bigger mounting screws - easier to tap the holes

Slightly more...

Are you sure they have the option of 24vdc and 80vac input? Those numbers don't match up.

Kern uses aluminium for the linear rail mounting I believe. They cool / thermally control all the mounting surfaces.

Have you measured your backlash? You need to check backlash.

The axes are defined with you standing how you would actually use the machine.

Side to side is X. X+ is the cutter moving to the right. Towards you and away from you is Y. Y+ is the cutter moving...

In my experience, wider is much easier. You can run out of room fast.

An important consideration is bend radius. You don't want too small / tight radius as it's bad for cables (radius needs to be...

You want diagonal bracing in the tube, not a horizontal plate. This can be done by stitch welding vertical plates within the tube at a few places and welding on end plates.

The gantry is subject...

The convention for axis labelling is:

Standing how you will use the machine:
X is left and right
Y is towards and away from you
Z is up and down

It is this way because that is how you design...