I have a Trek Stache 9 29+, and a Trek EX Fuel 650b bike.
Been thinking about getting a pair of boost wheels built up for the Stache 9 to see if the 650b plus would be a better compromise.
I really like the 29+ ,but it does have some drawbacks, and a change to a slightly smaller wheel size could be near ideal.
Given that I might go for alight wheel set up on 650b plus, carbon rims, tubeless and less true mass it might alleviate some of the disadvantages of the 29+ ( every bike has some flaws).
Disadvantages of the 29+ is going uphill.
You can feel the drag, it’s not that terrible, but it is there and it harder to accelerate . Riding uphill on a technical climb takes more effort, as the larger wheel can tend to stall if you don’t have enough momentum while minching your way up.
Can tend to wander on the slower climb as well, just a bit more physically demanding.
Advantages are the ability to maintain your speed on the flat or downhill. Easier to accelerate downhill, ability to roll over a lot of ground easier.
Excellent confidence in the larger tyre.
Have to have a look at what effect the 650+ tyre would have on the geometry.