Recommended · for beginners
Bluetooth 2.0 VS Bluetooth 4.0 (BLE) || Is an Upgrade worth it?
Why people recommend it
Suggested by helpers answering Arduino Bluetooth questions, as it compares the HC-05 and HM-10 modules and supplies source code to learn from.
Watch for: Handy when choosing between the two modules
In their words
Also check this video, you have source code in the description.
Pararera on arduino.stackexchange.com, Nov 2018. CC BY-SA.