The thing I hate the most from switching themes over and over is that when I swap themes, I have to re-organize the apps the way I want them, and hide etc...
You load some third party themes onto your device. Once you use a theme and set it up to your liking, the settings remain unless you uninstall it from the device (or change to a different theme, because the set-up is independent inbetween themes)
Any new theme needs to be configured to your liking. So, if you load "Theme A" and set it up and then you load "Theme B", you will need to set that one up as well.
If you uninstall either "A" or "B" then you lose the settings for the respective theme. If you keep them installed and switch between them, the settings will remain in tact
is there a way to lock the icons, so I dont have to re-config it?
Not on a theme that has yet been (Active), no. The creator of the theme has no idea where or what you want on your home screen. At least most of them are able to be customized!