With SRAM’s 360 % cassette, I think you can ride in mountainous terrain no problems. The only thing is that the gearing is slightly on the sporty side, i. e. with the 42-tooth chain ring I am missing my 34:32. But my easiest gear, 42:36 = 1.17, is easier than 34:28 = 1.22, so it is still alright.
Even when I rode 2x on my previous road bike, I‘d always stay in the big chain ring on undulating terrain, though. Especially on undulating terrain, having to change chain rings would drive me up the wall.