This machine is not ment for build and forget, it always needs adjustments and fiddling around.
If you take a look at any 3D printer community with self assembly printers you will see that even with identical aluminium machined parts everyone is getting a different result. Something that worked well for him doesn't mean that will work on you.
For example in linear rails if they are good quality on the undriven side gantry won't jog noticeably but in your case it might be.
Precision depends mostly on the motors, one step skip and it's gone because they don't have encoder for closed loop control.
3D models are available somewhere in the links that I have posted before.
Building a xy plotter is the easiest part of the process.
Assembling a 3D printer may take a couple of hours for someone unexperienced, finding the best settings may take weeks... (And we are talking for exactly the same hardware with thousands of other users)
Without machined parts settings will be all over the place, drifting, etc...
I would suggest to try to design your own parts and you will see on what parts/faces you need precision