You don't need wavefront (or any other path finding) if you build something that just methodically walks back and forth, moving up/down a little bit per iteration. Wavefront, and other path finding, requires a sophisticated understanding about the environment that you can't really build into an AVR microcontroller (nor run the necessary sensors for.)
Btw: The difference between an Atmega328 and an Arduino Uno is only the PCB and support circuits; it's the same CPU, it can do the same things and has the same I/O.
Finally, if you're planning on building a small wheeled rover that's held to the side wall through magnetic action with the inner scraper, then light weight and simplicity is your main goal.