The 1.9:1 ratio Shimano state is to be honest, more covering their arse than anything else. It’s to cover them against people weighing 20 stone that ride with all the grace of a Rhino, stomping on the pedals and stripping the clutch with every crank turn.
The lighter you are, and the less torque you apply to the pedals, the safer you will be going further below the 1.9:1 ratio.
Roughly around 1.6:1 seems to be where the majority of riders settle on in my experience, though as you’re riding a 29er, I’d definitely go with the 22T on the back as the 29er wheels are 10% bigger than 26″ anyway so alter the gear ratio to suit.