Pattaya and Jomtien are very similar as they are next to each other and the main attraction is the bar girl scene with a lot of sex tourists. I wouldn't swim in the sea there either.
Hua Hin is a nicer place IMO with cleaner beaches, but the population is mainly retired expats.
Phuket has a bit of everything including a lovely old town and nice beaches.
Krabi is lovely, but I think it would get boring quickly if you lived there and the main resort area gets very busy in high season.
Koh Samui has a young vibe and nice beaches, so it could be a good choice for you.
Places like Samui, Krabi and Phuket are much more expensive than Pattaya/Jomtien/Hua Hin, if that is a consideration.
As others have stated, travel around and see where you like.
If you are over 50 and intend to apply for the non o retirement visa, it makes sense to apply for the visa before you come to Thailand for a couple of reasons.
1. It makes it much easier to open a bank account in Thailand.
2. You do not need to have an onward flight booked.
you were lucky, but as always this is Thailand so it varies between offices. When I did mine a couple of months ago, I booked and there were about 30 people waiting when I got there! Without an appointment I doubt you would have been seen that week!