I spent about 3 weeks on Phuket at the start of this year travelling the island by motorbike trying to find the ultimate hammock hanging spot. Live was tough then.
The best beach resorts are without doubt near the airport. I didn’t go north of the airport though. Phuket town and Patong I’d avoid if you want some quiet time; I spent New Years on a beach in Patong with a pal and it was fun though. There is not a huge amount to see in the centre of the island, a massive Buddha and a lame waterfall from recollection.
I didn’t think Phuket was that great though when compared other places I Vsited in Thailand whilst being a bum for a bit. There’s an island called Ko Chang near Cambodia, now that was lush.