Rotating nuts are the correct choice for that size. 2020 screw is small for the long axis / according to me/ . I used on mine 2510 and rotating nuts. 400w servos are just the right choice in that case.

Bolts? Mehhh, for that size. It will be difficult enough to level everything and bolts will lead to the everlasting suspicion if sth has not moved. You can use bolts and pins, but anyway, my advice is weld it.

1.8 kw is small for that machine. 2.2kw as minimum, 3kw better.

Maybe read my second build log so you will get all the info there on 2600x1300x200 machine.

Again- for such a big machine to be precise, its not a small feat. Dont start the build before informing yourself. You will see that i have spend 3x 200 euro on epoxy before i learned 100% how to make it properly. its one thing to think that you have made it properly, its another thing to compare it against 2m straight edge and dial indicator.

There are only 700kg in my machine frame and it will stand on 2 or 3 legs without any distortion or twist / less than 0.05mm measured/ . Gantry weights 180 kg and flies 20m/min at 3000cm/s2 accelertation. Its not absolutely necessary to make the Z like mine overbuild, but gantry must be similar for perfect aluminum finish.

That frame you show is at the most for foam and wood. Not aluminum. Its incredible how shaky and bendy become things the longer they are. a piece of steel that 2 people can not bend at 1m at 3m you can bend with one finger.