Ingame MS or lag has NO relationship with the MS delay you use for your macro. The only similarity is that these are both measured in milliseconds.
The standard GCD is 1.5 seconds - your haste. Let’s ignore haste for the moment to simplify the maths. 1.5 seconds = 1500 MS. That means that when you do a /cast there is a minimum of 1500 MS between that one and the next one.
If you are using 100 MS for your macro it means that every 15th line in your macro is executed. If you are using 50 MS it means every 30th line. At 10 MS it’s every 150th line.
People have seen ingame MS and tried to link that to how fast their macro should run. They have also seen dovumentation on a thing called the spell queue and tried to link them all together. It’s utterly completely totally incorrect. Ingame MS won’t change how many lines of your macro are skipped between GCD’s.