IMO Koh Yao Noi actually has some of the best easier routes in thailand. Its a very quite island, with real thai locals doing there thing. Big tree wall, The Mitt and Grateful wall are all great.
The easier routes at railay/tonsai are polished, yet there are definently some good ones. 1-2-3 is good once the guides leave (approx 5pm). The keep is an amazing cliff. Wild kingdom / the nest is fun but polished. Fire wall also suffers from polish and constant crowds. Eagle wall is really good. Thaiwand wall has some of the best easier routes. Tonsai beach is only really good 23 and above. Basically, there is alot of sectors that you can work depending on shade. Avoid the sun at all costs! If you want to avoid the crowds try and get up early and avoid the guides...
Phi phi is an "ínteresting" island. The town is very busy and full of drunkards wanting to fight. If you do go try and stay out of the city. I could barely sleep with all the noise. The climbing however is really good @ drinking wall. I never went to tonsai tower, but i heard it is good too.
Never been to Lao Liang, but have heard good things about the climbing.