My DH just used a "hangman products" 18" which is rated for 200lbs. It was really easy and the product is very sturdy. It was about $11 at Lowe's. I think they make them rated up to 300lbs.

As long as you are in the stud too, both should be okay.

When we had our handyman hung a very heavy mirror over our couch, he used "cleats". I think if you google "cleats to hang heavy mirror", you can get more info.

I use those "ook" brand metal french cleats all the time, they're great for this kind of thing.

Ditto to TexAsk's recommendation. The Hangman product is a metal cleat system. I have used other versions of Hangman products to hang a heavy framed piece of art, and they were also cleat systems. Very sturdy.

The cleat system is a 2-part thing: One piece attaches to the wall and another to the back of the item you are hanging. They interlock. The Hangman website shows you what they look like.

You'll want to make sure you find either metal or wall cleat systems that will work with the hanging wire UNLESS you can actually drill into the back of the frame (the wood frame, if there is one) to attach a "regular" picture frame cleat. There are ones labeled for mirrors.

And you will probably need at least 3 people for the job. You want 2 people to hold the mirror up against the wall before you drill any installation hardware in, while you stand back and make sure it's in the right spot for you. Don't try to do it yourself!