cdflasdkesalkjfkdfkjsdajfd and the current profile is correctly closed when I switch to the other profile even if the new profile isn't the main profile?
To achieve that, you'll need to disable the toggle "Allow running in the background". You'll find it in the main profile Settings > System > Multiple users > the user you want to customize. If you disable it, then every time you leave the profile it will get logged out, and be left encrypted at rest.
cdflasdkesalkjfkdfkjsdajfd Also, I can power off the device from an additional profile or best to go to main profile in that case?
It's absolutely fine to power off the device from an additional user profile. When you power back on you'll be returned to the main profile.