The dispmanx video driver for RetroArch seems to be in somewhat of an unfinished state. I recently switched over to it myself to reduce latency and the first thing I noticed was that the onscreen yellow text was no longer visible. This is such a key element of RetroArch that you can bet the libretro guys aren't through with it's implementation yet. How long it will take to finish it up is anyone's guess and there is always the possibility that it will remain as is, but after switching to a wired controller and dispmanx, I personally believe the trade off is worth it for the more responsive controls. Otherwise beating hyper-sensitive control scenarios like the turbo tunnels in 'Battletoads' would be an impossibility.
Please do not post a support request without first reading and following the advice in https://retropie.org.uk/forum/topic/3/read-this-first