I've a few friends who swear by them, but I found a decent set of earplugs on Amazon which are "tuneable" - there's a bung and pin arrangement which allows you to set different levels of sound damping, and what frequency it centres around. Great for when I'm doing noisy concerts!
Yes, absolutely this. I used to dread taking hen parties off in the coach - they were generally much worse behaviour wise, then stag parties. And usually a bit handsy as well.
I would say the majority of kids diagnosed with autism I've had interactions with over the years have had ear defenders to block out noise, but just occasionally you'll get one who doesn't like the feel of things on their ears, or shoes on their feet, or trousers on their legs in the case of one Beaver!