What hub do you want to use? Flipflop or not?
Chances are that it will have a 42 mm chainline. See if your chainstay allows you to go 42mm with the chainring you want. If it does, go 42 for simplicity. Track bb and track crank.
However, getting a road crank and a shortish bb will prolly be cheaper. 45ish chainline, which is a bit trickier to match with your hub.