If I have VIA json can I create QMK code myself?

I am looking to buy a budget QMK compatible keyboard. I see VIA and QMK being used interchangeably. I feel QMK is more powerful as you see the source code and also modify/add features if needed in code. My issue is all the Chinese keyboards like epomaker, cidoo, etc. only give you VIA json no QMK source code, is there a way to create QMK yourself from VIA. Also can GMK67 ever be QMK compatible?

The easiest answer to the question if you don’t have the source code for it is No. The VIA json file doesn’t contain what is needed to create a QMK firmware from scratch

QMK supports a lot of different MCUs/architectures but if the chip or architecture is not currently supported then you are kind of out of luck if the chip isn’t closely related to an existing supported chip. If the MCU is based on 8051 (SinoWealth, BYK916, CH555, …) then QMK will likely never support it. Best way is to see if the QMK github repo have the keyboard before buying it

SonixQMK is a fork of QMK which adds support for some Sonix based MCUs, they support quite a few budget keyboards

I tried to find if GMK67 is supported already but it seems to be based on 8051 and isn’t supported by QMK nor SonixQMK. I found a experimental WIP project for it but it may not be functional at this time GitHub - vuhuycan/qmk-8051: QMK for 8051

That clears up some questions, thanks a lot!!
Ye, I think a short answer is to just go buy something that’s already on the QMK repo. Sucks since most of the keyboards there are super old/niche so never in stock and the ones in stock are very expensive including shipping.

The only budget ones I could find is kbdcraft adam (but that pcb doesn’t work with any other case in the market), same with bm60/65 and kbdfans 67 lite which is expensive as a barebone kit.