How to do the right thing under different conditions for the template?

Question

Layout

Hello!
The template (for mobile) after authorization is slightly modified, for example, instead of a logo image, an additional menu appears, instead of a brief description at the bottom of the screen, an online output appears there, an appeal to support.
So the question is not about how convenient it is for me, but how CORRECT (as is customary) to do: in one template, prescribe a condition for displaying content for authorized and unauthorized OR load different templates without porridge with conditions?
Thank you.
ps I like to shorten everything, so at the moment I have a mess (working) from one template with conditions, but you need to know how to do it right :)

Answer 1

Make separate pages if you are a coder