Hi and welcome to the forums
When you say your BG rose to 12.2 "while eating" is that measured via CGM? How long after eating?
Normally it takes about 30-45 minutes for carb to be digested to glucose and to start arriving in your blood. The "peak" figure is just a measure of how efficiently you digest carb, in my opinion, it doesn't tell you all that much. A small latte will take me from 5ish to 9.6 in 30 minutes, and back to 5ish by the hour. So what you're really interested in is how quickly your insulin response system deals with the surplus glucose - which yours seems to have done. 5.5 is bang normal, a bit better than "healthyish".
Decisions about food are very personal, and depend on not just on one item but on the other things eaten. For me, with a target of 20-25g carb per day, I wouldn't consider the sandwich at all, because it alone wipes out my day's ration.
It might give you some added perspective if you have a look at this small study paper which gives CGM profiles for a number of non-diabetic people eating higher- and lower-carb meals. Rises and falls in BG in connection with eating are normal and to be expected, the more so when carb levels in food are higher.
This study investigated continuous glucose profiles in nondiabetic subjects. Continuous interstitial glucose measurement was performed under everyday life conditions (2 days) and after ingestion of four meals with standardized carbohydrate content ...
pmc.ncbi.nlm.nih.gov
