Getting 10 Miis at once with Netpass is possible, with the previous version I was getting like 10 every hour. With the latest update I've been getting less though.
You can delete any mii from your plaza. Simply select them and click "Delete". You won't even see their messages again unless you Streetpass them again, though.
With the servers down I doubt anyone will see a legitimate blue light anytime soon. I don't mind what the colour is, I just don't think it's that farfetched for someone to want their Netpass notifications to be blue especially if it's capable.
So the same thing was happening to me with my New3DS and I thought I was going insane until I saw your thread.
I think I got a solution though.
Turning off "Enable loading external FIRMs and modules" in Luma by holding SELECT before booting made my shutdown speeds return to normal.
When I had it...