@kokokool As I mentioned before, I have the following test report

Peripherals and Bluetooth devices (Using a BT dongle)

2.4 Ghz Gamepad = Zero input lag detected. BT Earbuds = Had to pair it via ssh, instead of BT GUI, as well as I had to install pulse audio bluetooth. However, since my dongle es BT 2.1 I sense a bit of audio delay, but no audio crackling or popping. I'll test Wiimote pairing (it takes a bit of coding before) if theres a lag to report. Video = I'm using HDMI output on a DELL LED 1080p at 50 hz. No signs of signal delay. Games/systems Tested 8 bit consoles = full speed, no sound glitches 16 bit consoles = full speed, no sound glitches (perhaps, I might test games such as DKC or Super Mario RPG to check max performance. Arcade systems ( MAME 2003 romset, FBA)= runs 100% accurate (KOF 2003, SF. Today I'll connect a spinner or a analog dice to test mapping in racing games such as pole position, etc. PORTS = Quake3 Ill runs 100% full speed (including Multiplayer-internet) if you change settings to "fastest" and set resolution at 1024x768. Impressive.

Hexen and Heretic = 100% fullspeed, no flaws

additionally I want to install retropie-Extra script modules in this machine. Wanted to try GMloader and try some apks as droidports.

32 bit= Tested heavy GPU PS1 demanding games such as, Tekken 3 or Wipeout. Both run at full speed without glitches. I'll test two more PS1 heavyweight titles to confirm this point

Sega Saturn = tested with lr-yabause. 20-30 fps max.

64 bit = this is interesting. I had bit of trouble trying to run Mario Kart 64. somehow my system reports two mupen64plus-glide64 as standalone (not libretro), which one of them worked directly, but with two issues: sprites missing at the beginning of the game (for those who know, the spinning nintengo logo appears completely and very detailed), but the menu whe you choose a car, lap, cc, etc, shows random squares so I had to guess pressing accept until I get to the racing part. the system works but at 20-30 fps.

PSP = I had trouble to compile ppsspp (standalone and libretro) on my machine.

Dreamcast = I will compile reicast today.

Kodi from Retropie-extras runs ok. Haven´t load a avi/mkv file yet
That's all for now

@E3L1 Not really, the packages you mention are alive and well on Raspbian Buster and that's not the reason RetroPie doesn't support yet fully the PI4.
Care to share a reference to the quote you posted ?