Choosing parts is quite personal, but here are few answers to your questions:
I know the 062(after trying a 256 and 041), and it is a great frame, very agile. Nobody had any issue with it.
Not sure about the MB01 kevlar inserts if they change that much, but if I remember well you will find one build here somewhere.
For the groupset, a 1x11 is a compromise, either you will suffer a little on hard climbs(bigger chainring) or your friends will drop you on the flats(smaller ring).
The Eagle has apparently the same range as a 2x10.
There are Eagle kits you can buy with the full set( ring, crank, derailleur, shifter, chain, cassette ) at bike24.com or r2-bike.com for instance.
An upgrade set is just the shifter, derailleur, cassette and chain. And you can buy a cheaper crankset.
I just canceled my upgrade kit order( after two months of wait, they seem to have gripshift sourcing problems in all web shops ).
First there is no cheaper alternate parts like for 1x11(shimano, hope, e-thirtheen, etc.)
I break a derailleur a year it seems, and the Eagle is so big, I'm afraid it wouldn't last long and it is so expensive.
And I'm now used to climb with my big ring
For the brakes it depends on your budget.
I'm a big fan of Hope's brakes but they are not cheap.
We've put the last XT ones on the bikes of my son and of my brother and I'm impressed how good they are for the price.
XTR were 90€ more expensive for just 90g lighter.
The full set XT M8000 is a great option to consider too, it looks strong to last, very well built, a littler heaver, but at a very good price.
For the saddle, if you like the SMP style(I do), there are fine ones on aliexpress.com either bare bone carbon or with a little gel pad, all in the 100-120g range.
For about $40-$50
I use them for 2 years now.
For the tires, I'm a fan of Schwalbe.
Rocket Ron for the wet season.
Thunder Burt for the dry.
Always snake skin and generally the fast 2.1" size.
Have a good build!