I think this is starting to make sense. The SY-88x, M320, the DGUN-2561 and the Lexibook Cyber Arcade are probably all the same chipset, which I imagine is something like the VT368/VT369. That would explain the SY-88x using VT168-style RGB555 colour palette data, as it's some hybrid between the VT168 and the VT32/older NES-based parts, which unlike the VT168 also has backwards compatibility.
I notice MOGIS sell a console, the M200, which has enhanced games that look much more like VT168 (there's a video of it on Taobao
here as well as NES games. This is probably also the same chipset, I have ordered one to dump.
If MOGIS are associated with Wellminds, who have various similar systems on their website, their list of platforms are "VT02、VT03、VT168、VT32、VT368、VT369、SPG220、SPG243、SPG288、GPL16218、GPL16258、ST2302、EM78P153". Obviously this is something VT, whilst it could be the VT32 I think the VT368 or VT369 is most likely.
They also mention WS109 series encryption ICs. One of the games lists for the M200 had "WS107" in the name of one of the games, which does make me fear these new consoles have some kind of authentication/encryption chip which will make emulation harder (but probably not impossible with some creativity...)