So, if I understand you right, if normal or small portions are eaten, then normally only carbs influence the spike in the readings. However, a large portion size of protein and/or fats could also cause a large spike in the readings.
Usually not. But let your test results teach you.
I could go to a strict keto diet and naturally restrict the spikes in the readings due to the low carb intake, as long as my portion sizes of the protein and fat are normal or small. Is that correct? If so, that could be considered easier than testing to see what carbs impact the readings the most. I do think that your method may be better for long term use instead of going keto all the time.
In my experience not practical. If one eliminates or reduces offenders - in my case this are carbs only - calories have to come from somewhere. One can't increase protein too much (otherwise gluconeogenesis of the liver kicks in, producing glucose from protein), fat in my case is the most benign. The testing is really for knowing how much low-carb or even keto is necessary, according to trigs results. Some have to go to the lowest levels of carbs, like not more than 15g per meal. Others might do good with much more.
Meaning, would it take 2 weeks or 2 months to see a considerable difference? Also, how quickly would it take to get your Triglycerides to go too high again?
Sorry for being the messenger of bad news, it might take a few months, or you might be able to reduce your trigs partially only. This is totally individual. Conversely, even one meal can up your Trigs again, affecting lab tests for 1-2 weeks.