There are a few nice spots on the Club Motorhome stopover lists.
There are loads of nice wild spots, for example lovely big layby just outside Stackpole,, sloping layby in Manorbier overlooking the sea and castle, we have used both many times with no issue and many others over the years.

As for CL sites, I haven't used them but many are good but can vary as they are run by the owners individually.
The campsite in Newgale is right by the beach and is nice, so is Whitesands beach campsite but isn't cheap.

The other organisation you mention who's initials are B.S, I will not have anything to do with them, the attitude of the owners is appalling, they make it clear they are only after your money.
What is worse though is that I have been in more than one pub, the car parks quite busy with motorhome's but after talking to the landlord they make it clear that I am the only one who has been in and spent any money or even introduced myself.
Funny they all seem to have B.S stickers in the windows.
One of the pubs I am thinking about is now only open 3 days a week because they cant afford to open longer, it will be closed soon I am sure, such a shame.