TOGGLER SNAPTOGGLE Drywall Anchor with Included Bolts for 1/4-20 Fastener Size; Holds up to 265 pounds Each in 1/2-in Drywall by TOGGLER (20 Pack)

If you can't find a stud use these: https://a.co/d/0giTsLjQ

I've done TV installs for the better part of a decade. Running a board between studs is viable, but also overkill IMO And may stand the TV off the wall more than you'd like. As far as weight tolerance goes, a single stud will hold the weight of the TV with absolutely zero issue I recommend exactly what you are thinking...placing the TV where you want on the wall, lagging into one stud with 2 lag bolts, and use these drywall toggle anchors to provide stability on the opposite side https://a.co/d/0b60OdJa Been using these for years and I love them! *Edited for clarity