WebKit2 is not that bad and it scores 386 for me (GNOME on Arch Linux) while on the same exact machine Chromium scores 505.
There are few APIs you could safely ignore on a Raspberry Pi, due limitations of the board itself (as example, no gyroscope). Few other APIs can be polyfilled (Custom Elements) and others like Service Workers are less relevant unless you are using a SIM card external module there.
More active is the Crosswalk one
https://github.com/crosswalk-project/crosswalk meaning somehow there is already a way to use Chromium on Wayland, it's just not so widely deployed so, unfortunately, SBCs running Linux on pure Wayland that drops weston's xwayland.so module don't have many choices.
It's also a matter of GPU drivers support, most SBCs have drivers for Xorg only so that XWayland is eventually the only option there to have acceptable performance.
AFAIK there was also an announced effort to bring Chromium to the Raspberry-Pi Zero which probably will have to work on Wayland so ... fingers crossed!
Best Regards