Welcome.
I'm not sure rooting is as common as it used to be, or as necessary, though it depends on the kind of customization you plan to do. The "health" of the rooting community depends on the device you look at. Some of our device-specific sections have sub-sections related to rooting, though there are other sites with LOTS more info on that topic.
As for what you can transfer, we have a couple threads that might be of interest -
https://forums.androidcentral.com/ge...e-android.html https://forums.androidcentral.com/ge...16-nougat.html
Emails are generally not stored on the device, so you should be able to get them all once you sign in to your accounts.