I reckon the Horizons are as big as I'd go on a 650 gravel/all road. Anything bigger, and things will start to get too squirmy and sluggish.
I've just started using the Gravel Kings. Still finding that pressure sweet spot, but they have a similar feel to the G-ones. 350g to boot.
Noice! Tempted to go back to 700 just so I can use them as well. I wish they came up a bit bigger than 38mm in 650, I'd be all over them like a rash.