For me, if you are OK with a 2X then you can't beat Ultegra for the money. IMO, the reason to go GRX is for the 1X option. I prefer 1X for off road. I believe that at the 600 level the GRX quality starts getting good, I think the crank arms on the 600 are carbon (although I could be wrong). I have 2X Ultegra on my road bike and the front derailer creates problems and is just messy. However, for bike packing you may need the granny gear.