if you are using Konsole, than you can change it in Settings → Edit Current Profile at Command:
If you using Yakuake you will find iit in Manage Profiles, select the Profile → Edit at Command.
Becaus your user shell was already Bash. Now as explained above, Konsole has a specific setting for each Konsole profile you may create and you need to set it there. It doesn’t follow the user shell setting. The user shell will be the one used for example when using SSH with your user. You can see what it is set for in the file /etc/passwd for my user it will be /bin/bash (don’t mess with that file manually if you don’t understand what it is and how it works).
I know it’s not really all that relevant to this thread, but why the change to zsh in the first place?
Mint and other distros have also done this and it doesn’t seem to have any benefit, at least that I can appreciate. I for one don’t like seeing “unprintable” characters in Terminal outputs posted here.
Graphical stuff doesn’t belong in a Terminal window, in my possibly old-fashioned opinion.
Sure. Though that’s nothing to do with ssh. Just your shell, on each host separately.
You can freely type PS1=whatever to change your prompt in bash. You are just using the Manjaro bash prompt default. The classic bash prompt has often been PS1=[\u@\h \W]\$ - So \u gets user, then hostname, and working directory. Exactly what you have, but it’s a little more complex with color and stuff.
But zsh doesn’t use PS1, it uses PROMPT[1-6] and more. And It’s even more advanced at handling different prompts contextually to boot.