Carshalton and Cheam are nice - they are known as villages and have quite a nice small centre. Cheam has a decent range of shops. Carshalton not quite so much.
Both have lovely parks, Carshalton has ‘the Ponds’ Carshalton Beeches to me has a little less of a centre.
Public transport wise I think Carshalton is the winner. You have the Thameslink trains as well as Victoria and an easy bus to Morden for the tube. Good choice of buses including the SL7 which will take you direct to Heathrow for £1.75!!!
There is also Wallington - larger town with more of a high street. Quick trains to London Bridge and a slower line to Victoria. Again on 2 direct bus links to Morden. I personally like the area between Carshalton and Wallington. Roads off Park Lane. You can walk to Carshalton or Wallington depending on if you want some practical shops or a nice trip to the park!
schools wise I only hear good things about Carshalton Boys. More mixed in the girls school. Cheam high school I have also heard good things in.
Glenthorne gets good results but have heard mixed reviews, similar for Harris Sutton.
Greenshaw is another grammar backup option - partially selective (20%)
I quite like South Sutton as well - walking distance to the centre but fairly leafy although doesn’t have the parks that you do in other areas so much.
There has been a big influx of people moving from Hong King to the area in the last few years - I think mainly due to the schools. My daughter is Y10 now but I think in her last 2 years at primary 4/5 joined in her year alone (2 form entry school) this has brought a number of restaurants and food shops.
There is also the large Wing Yip centre not far away.
Carshalton has large public Leisure centre with pool in centre of village.