Carbon and I love our 1x drivetrains, and would have swapped if the bikes didn't come set up this way. We never seem to run out of gears; i think 2x10 only gives you 2 more gears than our 1x11. We even changed our 30 tooth front ring to 28t and we still don't top out. On the downhills of the last paved road section of WT, I was spinning fast but didn't quite run out. I wasn't sure if it would work for AR but it did.
I think in our flatland area the std is 32 or 34 front. Kona rep recommended the 34 and buy a 30 to swap out if req'd.
Yes, the size of the front ring would also correspond to the wheel size - a 29er would use a slightly smaller front ring than a 27.5 in order to compensate for the larger wheel diameter. Out here they typically come stock with a 30 on the 29ers and a 32 on the 27.5s. I was happy with stepping down from 30 to 28 on my 29er out here in the Rockies but didn't think I would need such low gearing for the race in Ontario. As it turned out, there were a few sections on the ATV trails that were steep enough that I was happy to have lower gearing... and didn't seem to give up much/anything that mattered on the top end by stepping down.
I wouldn't plan to have two different front rings and swap them back and forth regularly (I considered that but didn't want to bother). Instead, see if you can figure out the one ring that works almost all the time and just stick with that so that you don't have the hassle of swapping rings. Also, if it were a 4 tooth difference in rings, you might want different lengths of chains (another hassle).
Next big thing is 1x12 with a monster 10-50 casette.
Of course you need all new chain, derailleur and hub. They even held a funeral for the front derailleur.
Interestingly Rocky has gone back to having 2x11 spec'd on their Instincts. Not sure why... perhaps because as the article says alot of people still want an easier gear and 1x11 is still a compromise in that regard?
When I look at the gear ratios for 1x11 and compare that to what I often ride in on my 2x10 setup I think for sure I would want a 28T front chainring (at least for a 29er - as CO says 27.5 would be different) yet no one specs their bikes that way. With 28t I am still losing 2.5 gears compared to my 2x10 - two hardest ones and half my easiest one. 34t sounds steep for a 29er - that would mean losing my 2 easiest gears vs my 2x10. I agree with CO - changing the rings is a hassle and you are not likely to do it. You are more likely to want your easiest gear than your hardest...
1x12 looks nice - it would cover the current range that I ride in better. There certainly are bike design advantages to getting rid of the front derailleur - chainstays can be shorter for instance. As they say plenty of bikes being made now without front derailleur mounts.
Lots to think about!
I agree Revy. More likely to want my easiest gear than my hardest.