New rider here. Cruising dillemma

So I am a fairly new rider. Less than 3 months of motorcycle riding experience. I have two friends who ride their motorcycles using different methods and been doing it for a very long time. Friend 1 : while cruising let's say between. 60 - 80 KMPH on highways, he accelerates to a desired Speed then Immediately presses the clutch and deacclelerates. When the Speed reduces then again leaves the clutch, accelerates to a desired Speed and again pulls the clutch and deaccelerates. He keeps repeating this. The rationale he gives is this puts less strain on the engine and let's the engine cool down. Friend 2 : same scenario, but does not use clutch. Only accelerates and deacceleeates using the throttle. Clutch is used only for gear shifts. Both are doing this for 10+ years, and swear by it that their way is the correct way. Can someone please share your opinion on the correct way? Or if there is a different better way.