there is a setting in the GUI for auto login under settings > SDDM
i would assume if you login to that user, using the preferred session type and then set it auto login, then it would always use that type for that user.
likewise for the other user.
but you lose the ability to lock your PC when you are not using it.
there is a little drop down in the SDDM that chooses the session type with autologin, but it doesn’t appear to work when you logout from one profile and then into another one, at least using fedora, the little chooser in the bottom left takes precedence.
you may have to set one session type as a default for use with that user and then every time you want us the other user you have to also change the selection box before you login.
that’s slighly better UX that having to choose the session every time, no matter which user login you are going to