I think it comes down to who will be using your cab, what space you have and how cluttered you want the CP to be
If its just you that will be using you cab you could get away without any physical admin buttons and just use shifted inputs (as long as you are using an encoder that supports shifted inputs).
That would give you the cleanest/least cluttered CP but its easy to forget exactly which shifted inputs do what if you have more than a few and you don't want to accidentally exit a game, overwrite a save state or open the config by mistake in the middle of a session.
Just using shifted inputs makes it even harder if you have guests playing on your machine, especially at a party. If you are just using shifted inputs you will be going back to the machine every 15 minutes or so as someone wants the game changing or they have exited by accident or something.
What I would suggest would be just to have enough admin buttons to control the functions that you regularly use and then use shifted inputs for everything else.
For me this will be start game, exit game and also volume up and volume down. The front panels of my CPs have the coin and start buttons on. I will then use shifted inputs for pause, save/load state etc.
Its easy to have an admin button for everything but this can end up being cluttered, confusing and can be a waste having a button for something you use once in a blue moon.
You also don't have to have your buttons on the CP itsself. You could have full size or smaller buttons mounted below the monitor, or in my cocktails case mounted in the sections either side of the CP.
Example of buttons below the monitor:

Planned location of my admin buttons:
