You can (and should) add multiple numbers. They can be any kind of telephone.
This is based on the section "About trusted phone numbers and trusted devices" in the article: Two-factor authentication for Apple ID - Apple Support
To see, add, or change your trusted phone numbers use one of these methods:
● On your iPhone, iPad, or iPod touch: Go to Settings > your name > Password & Security. Next to Trusted Phone Number, tap Edit.
● On a Mac computer choose Apple menu > System Settings (or System Preferences), then click your name (or Apple ID). Click Password & Security, then add or remove a trusted phone number.
● Using a web browser:
1) Go to https://appleid.apple.com and sign in.
2) Follow security options until you find one letting you change trusted numbers,
3) Click "+" to add a new number (you may be required to verify this number).
4) If you wish to remove an old number, click "-" next to the number.
It’s a good idea to have multiple numbers available (ask a friend or a relative).
To see how to get a verification code and sign in with two-factor authentication' click here --> Get a verification code and sign in with two-factor authentication - Apple Support
If you have a trusted device running iOS 9 and later, OS X El Capitan and later, iPadOS 13 and later, or watchOS 6 and later, the verification code is displayed automatically on your trusted devices.
- Use a Trusted Device: Mac, iPhone, iPad, Watch. Code is either generated automatically or manually using Settings on the Trusted Device.
- Text or phone call to a trusted telephone number (any telephone; even landlines).
- Get a code from an Account Recovery Contact --> Set up an account recovery contact - Apple Support
- Instructions at the end about what to do if you cannot get a code and need to use account recovery.
By the way, no, you cannot turn off two factor unless you only just now turned it on, in which case you have 2 weeks to turn it off.