Can I disable the buttons on the left side of my iPhone 7 Plus?

You can't disable the mute switch.

In Settings>Sounds>Change with Buttons, you can turn of the ability of the buttons to affect the ringer and alert sounds. The buttons can still be used to raise and lower the volume of music, videos, games, etc.

Not that I know of. If it really bothers you, you would have to physically insert something to prevent those switches from being moved.