Seems that the game uses Unity type settings saved in the registry. Computer\HKEY_CURRENT_USER\Software\Bohemia Interactive\Ylands
I'm not sure how one would change that to force vsync, if that's even possible.
Would really appreciate if this could be answered or looked into. My FPS is constantly 120+ with my screen being 60 Hz. My graphics card is being put under unnecessarily high strain. Like the OP I wasn't able to force it with AMD's Radeon software.