I kept with the IPAC and UltraStiks but modified the approach with my arcade cabinet. I now have two Launchbox/BigBox set ups. Upon boot, it loads up a meta BigBox where the user can select from only a few options like Arcade games, Steam Big Picture, Street fighter V, YouTube music, YouTube Premium, Netflix, Shut down. The "Arcade games" option loads up a new BigBox set up (and kills the meta one) that just runs mame arcade games.
For almost all Steam games I use a wireless xBox one controller after selecting Big Picture. So, apart from Street Fighter V, I basically gave up on trying to get Steam games working with the cabinet set up. This was partly because of how hard it was to get them set up and partly because most games I had are not designed to sit at an arcade cabinet and use arcade controls. The games play better with a gamepad and when relaxing on the couch in front of a large TV. My cabinet has a HDMI connection to a TV for this.