At least in my experience you would only encrypt the fields that are sensitive.
So of course anything related to payments, possibly emails/ips, that type of stuff.
In a lot of services you don't usually need to refer to these fields except on the settings pages and possibly a checkout page, things like that. So the Username, preferences, and content of your site will likely be unencrypted.
Because you can avoid using those types of fields on most pageloads/api calls it should have minimal impact, especially since those places often include using an external api you have to wait for anyway (email, checkout, etc).
So of course anything related to payments, possibly emails/ips, that type of stuff.
In a lot of services you don't usually need to refer to these fields except on the settings pages and possibly a checkout page, things like that. So the Username, preferences, and content of your site will likely be unencrypted.
Because you can avoid using those types of fields on most pageloads/api calls it should have minimal impact, especially since those places often include using an external api you have to wait for anyway (email, checkout, etc).