Sorry for the basic nature of these questions ... I used to be an MCSE, but my mind is boggled by the capabilities of my phone.

I know I can use the GPS function with some apps to get current speed, average speed, distance for bike rides.

I use a Samsung Galaxy S4 running Android 4.4, and the web says it can connect to both Bluetooth and Ant+ devices.

Is there any advantage of one protocol over the other for a recreational rider?

What are the advantages, if any, to using a speed sensor instead of relying on the phone's GPS for speed? (Other than being able to track 'speed' on a trainer....)

Suppose I use the GPS to track speed and get a cadence sensor to track cadence? Is there anything meaningful that I'd miss with that approach?

Are there any budget sensors that work well - no freezes, easy setup, fast response, durable?

Are there any budget sensors that should be avoided?

I'm looking for a free app that is primarily a bike computer and which requires only the GPS feed from my phone (I don't want to incur any data charges) - any recommendations? (I don't want audible turn-by-turn directions, for example.)

I'd like to be able to get: 1) current speed, 2) average speed, 3) max speed, 4) trip distance, 5) total distance, 6) cadence, 7) clock-time for a ride, 8) riding time for a ride. OTOH, I'm experimenting with the 'bike computer Co' app with my phone in my pocket. After decades of riding with a computer on my handlebars, maybe real-time info is over-rated.

I have no desire to sync with social media.

Thanks in advance.