Oh lucky you. actually Xiamen is ranked the cleanest city in China...last i checked. Live there when not in USA or visiting Wifes family in another part of China. Shanghai is different, there are not as many clubs in Xiamen, Xiamen is slower than Shanghai...but most other cities are if they are not one of the big four. The beach is not bad either, piano island is a nice place to visit. Of course, there are not so many scenic places to visit as Shanghai. The weather is nice...I liken it to Los Angeles, it doesnt really get that cold nor does it get too hot. If you're in a better neighborhood, you'll most likely have a garden with a small lake or be near the beach of some water...take care to have some Off in the summer, to ward off the mosquitos...even on the 23rd floor. If there is something specific...i might be able to answer. To help more...one would have to know what you were into...or your lifestyle...Its no Vegas or Beverly Hills, like Shanghai and Beijing can be I'll tell you that.

I doubt there will be a big adjustment but regardless a few adjustments are necessary. You have one city that is smaller Xiamen compared to SHanghai. Less crowded and less popular although rather cleaner and more well suited for the more older expats. You just have to get use to the general area as always there will be adjustments but in this case not overly big adjustments. I think once you find everything you need like shops and places to go for your usual daily activities  everything will be fine! 

I visited once during the summer and found it to be very clean. However, it is also very hot and humid.

Also, I dont know if you have dogs or not, but I believe that getting a dog license is expensive.

In Xiamen I saw a very interesting puppet show, where one of the puppets actually fired a bow and arrow! for real!

Best of luck!.