Scientists discover a surprising link between Vitamin C and brain health

Ascorbic acid is the same chemical whether it's natural or synthetic. In a supplement it is highly purified, so the processing does not matter. The biggest risk to you is that you keep it too long and it will oxidize into a harmful chain of substances. Also, one has to remember to drink sufficient water with it, otherwise it can be caustic to the esophagus. 500 mg twice daily works very well. Stick to small bottles that are not kept open for too long.

Food might have mineral ascorbates, but these are absolutely not necessary. Moreover, mineral ascorbate supplements come with a plethora of questionable additives, so it's best to avoid them.

I strongly advise against liposomal vitamin C. It is a very unnatural and powerful form. It irreversibly gave me white eyebrow hair at a young age. It also led to skin reactions. I wouldn't wish these reactions on anyone. It can oxidize very easily and quickly. There also is a risk of atherogenic activity from the liposomal form. Vitamin C absorbs perfectly fine without requiring a liposomal form.

Don't pull all your eggs from one basket wrt antioxidants or you will regret it. If you want more benefits, look at other antioxidants.