OK so should anyone encounter the same:
Changing from opengl to sdl2 did resolve that last issue.
A Pentium G3258 at 3.2 Ghz has some speed issues, but it works fine with 4.6 and up.
Skylake or newer Processors should do with less frequency.
@mitu Thanks! I think I isolated the issue though: The refresh rate. I'm not sure why, but with the Pi and the same 32" LG monitor -- smooth at 60hz. When I adjusted the monitor to 50hz and set libretro to match the 2048 sample deviance went down dramatically in all the impacted emus. But I also tweaked a bit too much to be certain that's entirely it -- but that's what it seems to be thus far.
If my fix is a red herring I'll give your advice a whirl too. Thanks for another triage tip!
The problem was that the pi4 has 2 "connected" outputs (given by xrandrs output), this means that the MODE_CUR array is increased by one (HDMI-1 HDMI-2), and MODE_CUR becomes aspect ratio instead of being the refresh rate, my solution basically looks for /primary/ instead of /connected/... but no clue if that will mess things up for others.
in keyboard mode and followed the extended guide on this forum. In this mode ES wont recognise it as a gamepad so I cant configure it in the menu.
That is strange! Because, even if ES configure Input Menu is telling you it hasn't detected a gamepad, pressing a "keyboard" key should get you through the configuration of the controls for player 1 (same as with only a real keyboard connected)! Have you tried pressing a button (mapped as keyboard key), or does the message that no gamepad was found had mislead you to assume that a keyboard cannot be configured via the UI? Going through that should give you a valid retroarch.cfg (as said for player 1), to add player 2 controls you still have to edit the file.
@huhogany Hi. where do i even find that line /opt/retropie....etc, etc? I am so lost and confused. Do I look for it on pc or use the pi4 gui screen? i have no idea where to find this. Is it a command line?
UPDATE: I got it to work. What I did...
Updated post fixes in vman 512 image... reboot
set audio output to headphones
RetroPie updates have nothing to do with the audio - it's the OS updates (kernel/firmware) that can affect it. Of course, using an experimental/beta driver might not be the most stable configuration at this time, so you might encounter issues with it from kernel/firmware version to another.