I keep getting all these quests to go start a settlement or whatever...is it better to ignore them right away, or should I start them then ignore them? I like how they say yea 'just around the corner from here' there's a bla bla bla....how the hell is Jamaica Plain 'just around the corner' from Sanctuary...

Well some are going to start new quests or are part of the main quest so you might not be able to ignore them all *shrugs*

Personally I make everything I can mine, strip them of anything craftable and dump it in my main base (redrocket) right now just have Sanctuary and Farm next to Redrocket with settlers, I set up things so they're happy and don't bother with them anymore while I explore the top NW corner of map to get an idea of how the game works and equipment from combats and such. I got 2 fixed traders and caravans are starting to come to Sanctuary so I can sell stuff I don't want to scrap or keep. None have a beacon in yet either.

Anyways, reasons why I activate settlements even I I don't populate them .

It's fine to ignore it, its nothing pressing. I personally find that they are becoming more and more annoying. Running around trying to figure out why happiness is going down in a place with everything, and 15 settlers, only to find out that one settler took another settler's bed instead of one of the 10 free beds... lol.