Is knowing the MTK processor version sufficient to get the right twrp image on Android device? If I download a twrp image depending on the MTK processor version and not the device name/ manufacturer, will I be wrong ? and will it be 100% working?

Note: the device is not rooted, I am actually trying to root it this way(No other way is working), so let's focus on the question.
It doesn't work that way.

TWRP depends heavily on the fstab of the device model in question, which describes the partition layout of the storage. This is not related to the SoC (processor), and almost never the same between different models.