Phones will always be worse for privacy. They are festooned with microphones, cameras and a variety of radios. The PC I am using to type this doesn't have any of those things.
You can't. "Airplane mode" doesn't actually shut down everything. Carriers can still track your phone. https://undercodetesting.com/how-your-phone-tracks-you-even-...
Your phone also still collects a record of your GPS data, and that history gets transmitted back the moment you have a connection. Your phone can also still be tracked via bluetooth while in airplane mode. That's also how "find my device" works when your phone in airplane mode. WiFi data can also be collected while in airplane mode.
Airplane mode is basically a lie. It's prevents the transmission of certain specific signals from your device, but that's about it.
The apps you use, sure, those are also optional, but using those same apps on a desktop would give them even more information about you and more power over your system.