I've only run the 817 RD up to 42T but presume by using a Wolf Tooth Roadlink you could get up to 46T. I actually bought a 46T cassette to try this theory out.
The 1x derailleur doesn't have the geometry to work very well 2x, don't do that. 38x46 is good enough for bikepacking, very long climbs there. Don't use road links if possible, they push the derailleur too far out.
You can do 42x46, but you'll be wishing for lower after 1 ride.
I've only run the 817 RD up to 42T but presume by using a Wolf Tooth Roadlink you could get up to 46T. I actually bought a 46T cassette to try this theory out.
Could you not stick a lower chainring on also?