Those seem to be for drywall. The strongest option is using resin to install some threaded rod, eg fis-v which is rated to 43kgf (shear load) in the lower of the two rated aircrete classes. That's because it spreads through the holes and therefore has a larger surface area of interface. The downside is that it's not removable.
That seems really low for shear. The M8 Rigifix say 245 kgf for 1mm displacement in shear.
Also I slightly misremembered the rating for pull-out - actually in 34 kgf, and they are applying a fairly generous 15% safety factor (i.e. tested ultimate strength was 224 kgf). But still, it sucks that you can't just use a normal wall plug and have to worry about this sort of thing.
That's 0.43 kN which is 430N or ~43kgf. Comparing to the rigifix table they are using a heavier aircrete and a smaller safety factor, which would take fix-v up to 80kg but that's still a big difference. I wonder if there is a testing methodology difference, as usually resin fixings are considered stronger than plug fixings.
If it's just a threaded rod held in with resin then I expect the difference is in the hole size. The actual wall plug for the M8 Rigifix is 16mm diameter. Also the M8 bolt is inserted into a larger metal sleeve so it's less likely to bend. I don't know if that affects things though.
