Hit the studs where you can and use Hilti 1/4in drywall anchors with Phillips screw for the rest. I used to install tvs and when we couldn’t hit a stud, we’d use these. If I remember correctly, they can hold a couple hundred pounds in 1/2in drywall. We used them to hang old school heavy plasma tvs so a new led won’t be any problem for these. You can buy them from Home Depot.