How to find a fitting drivetrain I'm currently building up a new bike from a vintage Scott Windriver MTB frame. My plan is to install a Shimano Zee 10-Speed drivetrain because I don't really need more gears in my area, I want it to be durable and there's a huge discount on it. But I'm not sure about the compatibility with my frame.
The bottom bracket is 68mm BSA and the rear dropouts are 135mm apart from each other.
My guess is that I need a FC-M640 crankset. It comes with a 68mm Hollowtech II bottom bracket, will it fit?
For the rear mech I can also choose between "23-28t Close ratio" and "32-36t Wide ratio". Does this concern the number of teeth on the biggest sprocket of the cassette? I rather want to have lower gears so would the close ratio be the right option? How does it affect the choice of the cassette?
And - last but not least - will I get a hub that fits my frame, the cassette and the rear mech? I'm not sure about how common 135mm dropouts are nowadays.

Thanks for any help!
135mm quick release hubs are still common. 26” 135mm 10 speed cassette compatible wheels should be easy to obtain.

Make sure to get a Hollowtech BB that is specific to MTBs. These fit 73mm shells and 68mm shells with included spacers, and are compatible with MTB cranks. Road Hollowtech BBs only fit 68mm shells. 

For the rear derailleur, "23-28t Close ratio" and "32-36t Wide ratio” refers to the size of the largest cassette sprocket supported. If you want low gears you want the wide ratio option and a 11-32, 11-34 or 11-36 cassette. Do some research or gear ratios to decide what range you need.