Welcome!
I left Kaiten some time ago when the developer started testing new features on the Google Play product. One day it worked the other not and he didn't fix things for weeks. As I use the mail for work, it's vital and got fed up with that kind of treatment. Found AquaMail after looking for other mail products and tested MailDroid. The developer is really responsive and the application is quite good. The first thing decided me on going Pro and started to recommend to fiends and coworkers. Most people have the same need as us. A simple, yet useful mail client that is well supported.
Yes, go to settings on the accounts screen and then to network. There you will have settings for mobile and WiFi networks. You can set to download only headers if you want.