So, i am not sure what happened. Like i said i made a hotkey for the fast forward button in the retroarch settings. After running games from other systems i was running into all kinds of problems, and had to restore my image, thanks for the input.
@dankcushions well, I have edited a few more configs and its all working fine. There is an option for resetting permissions - which I thought may have been the solution - if it happens again, that's what I'd probably try - because once it created the file itself it seemed to me ok.
For me if I used swapchain = 2 in conjuction with runahead, even with threaded video still left enabled, I'd get severe hitching in several games that I tried. Alien Soldier and Disney's Aladdin being the two that I tested that made it clear to me that I just had to leave runahead and swapchain at 3 for that core. Video threaded being disabled seems to be fine with those settings though.
Disney's Aladdin is an interesting rom (and nice to play :) ) - there seem to be 4 frames of internal latency in the game [edit: no, there is only 1], so the lowest latency working configuration that I had was to set threaded video on (the default), swapchains at 3 (the default), and use 4 frames of runahead (which I tested in single instance mode/second instance = no)
[Edit: It plays OK with 4 frames removed, but when I stepped through a frame at a time I can see that removes 3 frames of animation after the button press]
That's with a shader running (I'm trying zfast_crt_standard.glslp - thanks for the suggestion)
I haven't found any situation on a Pi4 where zfast_lcd_standard.glslp allows me to run anything that crt-pi didn't yet.
It looks like it was the difference between using mame2003_libretro.so and mame2003_plus_libretro.so. I had copied mame2003_libretro.so from the regamebox distribution to the retropie distribution by mistake when I was testing to see if that file was the difference in performance... As can be seen above by my documentation of the command which runs the emulator in regamebox, it uses mame2003_plus_libretro.so.
So, to recap, if you are experiencing the usual slowdowns with double dragon while using retropie distribution and would like to eliminate it, you can just copy mame2003_plus_libretro.so from the regamebox distro into retropie wherever mame2003_libretro.so is... and of course have the settings set to use mame2003_libretro.so. Also, i assume if you install the mame2003_plus core and instruct retropie to use it, the effect would probably be the same.
Hope this helps someone out, I know there is lots of talk about laggy double dragon, and there really is no fix because it is emulating lag which was present in the actual hardware of the arcade cabinet... i've seen posts saying to use the bootleg version (ddragonb.zip) because it was built on better hardware, but this looks like a solid and more appropriate approach to fixing it!
Answered my own question. So my workstation has 3 monitors and a TV, the pi had this issue with the TV and one of them monitors. Works absolutely fine on the other 2 monitors though, and the TV in my living room where this was going to go anyways works fine with it as well.
Hey dank, thanks for the heads up; I kinda figured they would be, yeah. I'm just using them as a basis to create my own such that the screen gets positioned right, ie. for the x and y values. I certainly wasn't gonna just lump them all in there.
While I'm here, did Naomi get borked in the last few weeks? Suddenly the ROMs I have for that don't work (since I had to reimage I mean).
You know what, never mind, forgetting so many things already done several times over: BIOS!