I built a front wheel using a Race Face AR40 offset rim last week. Using the Race Face published ERD (600 for a AR40 29+ rim) and Shutter Precision's published hub specs in Spocalc, the calculated spoke lengths put the ends of the spokes right around the bottom of the screwdriver slot. I definitely have a bit of margin left before the spoke is flush with the head of the nipple. Spocalc gave me 292.2 and 293.7 so I went with 292 and 294 Sapim Race double butted spokes and brass nipples. I have the rear laced up (same rim, Hope hub) but I just discovered that my rusty old TS-2 truing stand will not accommodate a 190/197 rear hub. Either I run a straightedge across my frame or I have to pick up a pair of the $55 extensions. Note that the thru-axle from your bike functions well as a truing stand adapter for your thru-axle hub.
Sapim HM washers add 1.4mm to ERD. I'm running them on both sides of the rear wheel to bring the calculated lengths from 293.3/293.5 to 294.0/294.2 so I can run 294s on both sides without worry. In a pinch, I could probably replace a 292 on the front wheel with a 294 and one HM washer.
Yes, stainless washers are stupid when they touch aluminum rims and/or aluminum nipples. Anodizing may help a bit by adding electrical insulation. This is my first build using them. I'll know more in a year or two.