I no you can not cook meat in this game but just wondering if there are any negatives eating raw meat then taking potions or a sarnie?.

No, they are all just sources of food, with varying (and limited) levels of health restoration.

As OP I really believed I could cook them, I suppose Gothic series is in part a source of that expectation, but I finally gave up never use them until I find how cook them, so it was the right decision. :-)

Limited levels of HP restore, in my opinion a design detail error. I'm no fan of Gothic 3 (unlike Gothic 2 with Nigh of the Raven) but G3 was full of good design details for HP management, and one of them was having food not usable in combats (not sure) and with HP percentage restoration.

That's probably why TW3 offers a skill to have auto HP restore, like a give up to make work the HP/healing/food system past the first parts, first levels.