regarding Bootouts:
1st measure (downsize outer boot dimension):
you can try to use a boot with smaller outline like Boot manufacturers Burton and Adidas provide.
(Adidas offers the smallest outline on market for a given Foot Mondopoint, Burton is second). Also try to get with the Boot Mondopoint as close as possible to Footmondopoint.
2nd measure, Binding:
use a Flow NX2 CX fusion straps , they are super stiff and supportive (new supportive stiff ankle strap 2022!) and have no heel cup to drag on snow and causing bootout.
I ride the NX2 CX straps on a Rocker Wide board with Burton Ions. Pretty happy with it, best combo for Piste Carving of wide boards.
Camber: this makes precise edge changes (slow FS BS edge transitions) easier and speed flatbasing (bombing) more stable, especially if your camber board is heavier and has good damping.
Regarding playful Butter carves and Eurocarves, Rocker has less bad influence than you might think.
I have still a wide Rocker in my Quiver for Eurocarving and Buttercarves, and it is doing fine.. Flatbase Bombing is more of an issue.. but I stay below 50mph with this board and take more care if terrain is bombed out or spiced with icy bumps and steps, it is fine.
for more locked in feel on your Rocker board try to file a steel edge angle of 0degree at base and 88degree at the side. And keep your edges sharp. (a good service shop may be the easiest way to get these precise steel angles on particular request)
So for playing around with butters and euros: keeping the proto and downsizing boot and using bootout free binding is an option.
If you say, I want to add stable bombing, then a heavy stiff camber board with good damping makes sense. But Butter Tricks are harder to learn on these boards.
And Downsize Boot and Bindung as much as possible, a 1.5cm wider board is much harder to ride, I would recommend this to do even if you chose a Knapton Custom board where you can get any requested waist width.
my specs:
Boot Burton Ion MP280 outer size 30.5cm
Flow NX2 CX Size L (for MP 300 change to XL)
board Voelkl Dimension Rocker 282mm min waist. (I guess the Proto Synthesis has some similarities but probably performing better than my old Voelkl).