So, I had similar queries to OP and decided to test out the orange mesh Toaks bag as a cozy in lab conditions.
I have the 1350mL UL Toaks pot and I poured 500ml (16.9 oz) of boiling water in and measured the equilibrium temperature at 92C (198F). I then put the lid on, put it in the mesh bag, tightened the drawstring and stuck in the refrigerator for 20 minutes (fridge temp measured with digital thermometer @ 6 C/ 43F). At the end of 20 minutes the water temperature was 72C (158F).
I'm quite pleased with this. THis is a good approximation to field conditions and For me, this is plenty hot enough to eat. If I'd been able to bring to the boil in the pot, I also probably would have had a higher starting and finishing temperature. Given that the bag weighs only 20g (0.7 oz) and doubles as a stuff sack for the pot, the toaks stuff sack seems to be lighter weight option than the average reflectix or ccf cozy (usually about 45 g/ 1.5 oz).
Question is, how much better is reflectix at maintaining temperature. I'm sure it does a better job, but the question is whether it is worth it for the (admittedly small) increase in weight and need to have an extra carry bag.
I would be super grateful if anybody is willing to carry out a similar test with their reflectix/ ccf cozy. Ball park figures welcome!