Am I right to assume that DSLR/Mirrorless RAW images do not benefit from the Drizzle, because they already come debayered? Meaning there is no real raw data to extract by drizzle, other than a simple upscale?
A lot of mirrorless camera produce real RAW images.
That depends on how you have set your camera.
Well, Canon has CRaw and Raw. CRaw is compressed (quality difference is negligible, if at all). I’m not sure if the bayer pattern is automatic there or not.
If it is, then debayering right away in Siril is the only way to go. Hence - no (real) drizzle.
Use RAW files, no CRAW