i dont even know if amidevcpp sports up to date c++ compiler. afair the last available version was around 3.4.x. on the other hand there is a c backend 4.5.0 by bernd, which makes it fine for a contemporary project written entirely in c as netsurf is, and likely therefore artur was able to compile it for amiga/sdl without major changes.
on the other hand whether we like it or not, a lot of stuff we desire is nowadays written in c++. i cant argue if c++ produces slow code, i know some claim that. the main question is though, do we want to try to port these apps even if just to see if they are slow or not, or do we resign on them entirely. from my experience with aros owb on 68k real hardware i must say it is not as slow as you might expect it.
as said, odyssey/owb/webkit is c++, so any kind of owb needs c++ toolchain. aros has it including 68k (4.6.2 afair). 68k amiga lacks it. perhaps someone can work out and provide appropriate devpacks for amidevcpp. id like to have amiga/aros68k 4.6.x. that might simplify the situation. but dont see anyone up to the task.