From someone who rides an agro hardtail, I would definitely be looking at 34mm forks if you at the 140mm mark but 120mm you could argue each way. Depends how aggressive your riding is.
Brakes, unless you are really pushing it, you will get shaken to pieces before needing 4 pots front and rear. Even with 2 pots, the biggest change would probably be the feel of the lever particularly coming from 2 finger levers. Magura trail sport are relatively cheap and would leave you with plenty of brake power.
Cranks as an upgrade meh, but look at a 30t on the front. If you use 22/36 then 32/46 won’t get you there. 30/46 would be closer but will also leave you short in the top end. While you are at it, a new cable and outer would make shifting excellent again
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