We have a house in Vero Beach. We spent about 10 years trying to decide where would be best--we are slow

I grew up going to the gulf side, but ended up preferring the Treasure Coast. We are on the island, so we can walk/bike to the beach and the Indian River Lagoon--great for walking, biking and viewing beautiful sunrises over the beach and sunsets over the lagoon. The beach is quiet, which is good with us. I also enjoy sea turtle season
If you want warm weather for the winter months, make sure you get far enough south. We enjoy the panhandle area, but it would be a little chilly for us in the winter months.
We aren't seasonal because DH still works so we are "in and out." We are there a lot, just not for long stretches. It does get busier in the winter months, but not horrible. We have found that going to dinner around 7:00 is perfect--no wait and we normally eat later anyway. I wouldn't try to eat at 5:30

I still haven't found the less busy time at Publix.
The City-data forums can be good for information on specific places. I used them quite a bit for all different types of information. Make sure to do your research--I'm sure you are

There are several people who ended up in places they thought they liked on the surface, but once they got there it wasn't what they thought it was going to be.
Enjoy your search!