> 1. Is MAME the backend for the arcade system, regardless of the front end?
Yes, MAME is always what runs the arcade games. On the Pi it's a version of MAME that's old enough to get a driver's license, and on a PC you can generally run current.
> 2. Are there recommendations for the front end? Obviously this web site is one of
LaunchBox and GameEx are two popular choices for that kind of setup.
> 3. Can I get Mame and the front end running and stable on this system: AMD A6 4400M
> APU with Radeon HD Graphics 2.70GHZ
That processor is going to be marginal for MAME and it won't run Dolphin (the Gamecube backend) well at all since it's single-core.