We went there last summer. There are a few places to SUP, I fancied the large harbour but only when the tide’s in and watch out for ferries 🙂 You can park by the old harbour and put in there. I can’t vouch for safety but they hire kayaks there and there people jumping off the rocks and swimming all around it.
There are many little coves to paddle in but don’t leave the shelter of the cove as from the top of the cliffs we could see that the tide flows pretty fast along the coast. 5 knots according to a local, so it’d be pretty hard to get back to your starting point.
As for surfing there are loads of spots. Beaches – Mwnt and Llangrannog are highlights IMO.