Just following up on this, went ahead and did the coding with RJ. Added the auto multibeam high-beam lights and the Distronic radar cruise. General note, the biggest pain was that they are in the UK so the time slots for coding are not convenient for US times. I wound up doing it with them at 2am, which worked out ok for me as I was awake from jet lag anyways. I think you can book roughly their 5pm to be your 7-8am? Wouldn't be awful then.
The multibeam auto high beams are super cool. This car already had the best headlights I've experienced, and I was already impressed with how fluid and seamless the light movement into corners was as you turn the wheel. The high beams are just as seamless, they turn on automatically, you don't really know when they turn on and off (other than the indicator in corner of gauge cluster), but you never get flashed by any traffic. The only complaint is they aren't sensitive enough to road signs up high and sometimes they stay on and glare off the sign quite badly, but that sensor may be confused by my window banner tint (I am not sure where the sensor is.)
For the Distronic, my GLS required swapping the button assembly on the steering wheel. Easy, clear instructions and YT video were provided, parts arrived from UK same week. I marred up the access hole on the back of the steering wheel when inserting a tool to remove the airbag, but it's something only I'll ever see and know about.
The actual coding was super easy. They mail you a programming dongle, you provide a laptop with Anydesk (and obviously need to have some data security comfort in letting some random stranger take over your PC for a while and do shit that is invisible to you). Laptop needs to have internet during coding, so you need to park somewhere with wifi or tether a hotspot. But then you connect the laptop to the car OBD2 via their dongle, give them the Anydesk code, they connect, and you just sit there and wait. In my case I had to turn the IGN off and on for a few seconds at one point in the middle of process, and then I had to immediately take the car for a ~15min drive without shutting it off when they finished so the Distronic radar could recalibrate itself. I think the coding itself took 15min or so, and then the drive. Was home and done in 45min, after driving around a bit extra just to play with the auto high beams.
Did a few other "usability preference" codes since they included some free coding credits with my Distronic, stuff like "remember engine stop-start setting" and "64color ambient lighting" - exciting stuff, I know.
Here's the full list of coding options they can do, apply to most modern Mercedes Benz:
https://rjautomotive.net/pages/coding-options