I have just hung a TV cantilever bracket using M6 Rigifix mounts (and 1 M8 in top centre where most of the pull away forces are likely to be).
They are extremely convincing and as claimed, allow stuff to be pulled up tight without crushing the plasterboard.
Only downside is the monster hole they need (12mm or 16mm). But they do at least have a data sheet with max load figures in various substrates (pull out force, recommended and failure)
The Dryline Pro fixings are a bit more subtle (8mm hole IIRC) and did the job for some chromed twinslot shelving below said TV. Less pull out forces, Rigifix would be overkill. These are more like a frame fixing but with the "spins in thermalite block" problem solved.
Not affiliated, just a very happy user. And yes, they are not cheap, but probably pale into insignificance with the cost of what's being mounted.
Tim