New Boy introduction

[Crunch]

Hi
My name is Paul,
I am right at the start of a cnc router build, I have been reading on here for some time now gathering as much info as possible,
This is all new to me so please be patient with me,I have a massive task ahead of me as I have no back ground in cnc at all, I've always been interested in engineering and fascinated with cnc. I spend most of my time tinkering with motor bikes , model helicopters, or anything mechanical.
I have a small lathe, which i have learnt loads from and quickly realised it is not as easy as the pro's make it look.
I'm learning fusion 360 cad and cam and watching as many videos as possible,
My build
Cnc moving gantry router all steel construction, it is based on image attached, but want to use 200mm x 100mm box steel for gantry ,fit ball screw inside and cut letter box for ball screw, ( I have a choice of 4.5mm or 8mm thick ), with the cut out in the front don't know which to use for strength purposes, also weight.
It's made from 70 x 70 X 5 box steel for the router frames,
It's 1200mm wide x axis and 1000mm deep y axis
20mm square linear rail X Y Z
1 x 2010 ball screws on x axis ( only because of what I've read, don't know if 16 will do ?)
2 x 2010 ball screws on y axis ( again what I've read to stop whip )
1 x 1605 ball screw on z axis
All with pulleys and belts, need help with ratios, nearer the time.
When I started to think about this build I was set on using nema 34 8nm closed loop stepper motors, as bigger was better, I soon learned that was not the case, and holding power number is not the one to look at.
The stepper motors is where I am really struggling as my machine will be heavy as I want to cut aluminium. But all this reading has been worth it as the one thing you tell new comers is not to buy any electrics which I haven't,
Sorry for the long post, I have so many questions but will ask as I need to.

Great forum, so much info.
Thank you Paul