@1
"You can not really calculate well in this time control." ++ Right.
"It's barely worth analysing because you simply didn't have enough time." ++ Right.
"I am always looking for big knockouts, trying to avoid blunders and spot tactics." ++ Yes.
"For an classical otb tournament, i am not sure if 10 minute game helps anymore." ++ No.
"Will I have enough opponents willing to play 30 min or 15+10 chess?"
++ Above 2000 it gets hard to get paired for 15|10,
though that is the official rapid time control like for the World Rapid Championship.
10|0 is officially still blitz, though chess.com calls it rapid.
But officially, 10:01|0 is rapid.
I don't think one second makes much difference, what does make the difference is that most people play right on the boundary between blitz and rapid.
(Personally, I would prefer it if there was a non-custom 10|2 time control, but there isn't so I use 10|0 instead).
That is true @Bobison123 you have to become good at all time controls (not perfect just good) rapid just isn't good enough it is too long
what do you mean rapid is to long? rapid is too short