All-around brushless motor/belt drive spindle question

Hello,
I'm currently building the moving bed cnc machine, using the THK linear actuators, KR46's for XY and Kr33 for Z. Working area is 400x400x22mm. The frame is aluminum 3060 profile, which I'm planning to fill with the epoxy granite.
I'd like to have a spindle which can be a good all-around solution, mostly for aluminum, some wood and steel.
That's why, I started looking into the belt driven spindles, where I can adjust the rpm and torque, by changing the pulleys, when needed.
By chance, found something on aliexpress, which fits the bill and looks up to the task: aliexpress.com/item/32961976754.html
It is ER20 spindle, with 5 bearings. The seller says, it's around 3kg.
But, I'm not really sure, which of the options will be better suited

https://i.imgur.com/04yEJ3w.png

I'm in between ER20(60)-4 and ER20(60)-6
The table shows all of them are using the same bearings, but, on the other site, for the same spindle, it showed different bearings are used, for different options.
Options 6, perhaps, looks more interesting, but has lower rpm.

For the motor, found a sensorless scooter brushless motor

https://i.imgur.com/57akKTO.png
https://i.imgur.com/HXyUrQl.png

Specifications:

- KV : 170
- Power: 2800w
- Voltage: 24-36V
- Install holes:30/44mm
- Diameter:63mm
- Lenght:70mm
- Shaft: 10mm
Weight around 1kg

Would appreciate, if I could get some guidance here.