Scouting Costa Blanca & Costa del Sol

First things first - the train only goes as far as Fuengirola once past Malaga going west.
I lived on a boat for 12 years just the other side of Estepona, so my experience is that side of Malaga.
There is a fair amount of coastal development, but it is not high rise or spreading too far inland.
Estepona is charming and largely unspoilt.
There are white towns inland from there that have a creative expat community eg Gaucin.
Going back eastwards , from Marbella all the way towards Malaga it is high rise tourism.
From my point of view, most unattractive.
The possible exception is Mijas Pueblo (not Costa).
Older houses have thick walls and small windows to keep out the heat.
Modern places and apartments have (largely) individual ac.
Power supplies are pretty good (except for last week!).
Properties inland can be quite good value, as older people are moving down to the coast for modern houses and access to hospitals!
The British expat community has shrunk a bit post Brexit.
You will obviously be doing your homework about residency and taxes.
This forum may help: https://www.costadelsolforum.com/
Or this:https://www.expatforum.com/forums/

We spent five nights in Denia last November and I imagine that small city would be a lovely place to live.

Thank you both for your replies! Duly noted and will report back once we've explored!!