I think you would get away without a backing pad for the fairleads on the bow.
There should be quite a bit of GRP to screw into. The position of the fairleads – close to the edge – probably means you cannot get a pad underneath anyway.
Use some self tappers to fasten, bed the fairlead with some sealant.
There is no direct pull on the fairlead so that should be fine.
For genoa sheeting a simple solution is usually good enough for a family boat.
These combined fairlead/jammers work pretty well;
Once you start adding ratchet blocks the costs go up – and you also use more space in the boat.
In terms of where to fix them, there is a photo here;
Assuming you have wood side benches then screws are fine to fit them – the screws will need to go about 3/4 depth of the wood.
I would advise against ratchet blocks on their own – unless you don’t like your crew.
hope that helps.