Not to pull away from the main topic, can I ask where you get the throat swabs? Or is it something you can only get through Npip?I don’t know anything about the vaccine except what I can read on the Zoetis site.
It is always advisable to quarantine even healthy looking chickens that you bring in. The exception is day old chicks from a hatchery which are most likely to be disease free.
MG is one of the major reasons to quarantine. It can have a slow incubation (up to 35 days I believe) so you need to set up a quarantine that will work for that long.
That said, if after a period where the incoming chickens seem healthy I have shortened the quarantine after getting a negative throat swab PCR test for MG.
The test isn’t perfect, but combined with a couple of weeks of quarantine, and healthy looking birds, I personally feel comfortable reducing quarantine below a month, and the fact that my starting point is a month will tell you I am risk averse when it comes to disease!