My experience of the folding grapnel is that grip is poor.
2.5kg anchor plus 3m chain plus rope is generally considered okay for daysailing e.g.
This design will lay flat so is fairly easy to stow.
For the length of warp 5x the depth of water you anchor in.
Of course the holding power is very dependent on the nature of the sea/lake bed. If the bottom is rock or stone and the anchor cannot dig in then you are relying purely on the weight of the anchor and chain. So whilst the weight of the anchor is a factor the nature of the seabed is equally important.
Something like the example above is fine as a “picnic” anchor, but a little light for overnighting in my view.
We carry as a main anchor a 10lb plough – but handling this weight is more difficult.
Whoever is going to do the anchoring/recovery must be able to comfortably lift the weight of the anchor plus chain.
Hope that helps