Thank you for your long and useful answer.
I use a Tacx Flow Smart with a Tacx training tyre. Of course in Zwift i ride a road bike.
I took a FTP test 2 days ago that I clearly failed because I didn’t understood how ERG mode works and I almost didn’t shift gear during the test. It gave me a FTP of 157 which is 2.5w/kg for me.
I know I need to increase my performance but globally I’m just surprise how people can produce output power very easily.
To give another exemple, it looks to me that 90 rpm is like cycling very, very fast but when I see people on their bike (on tv, youtube, etc…) 90 rpm look very easy and “slow” for them.
I’d say that my question is more: if I buy a road bike will it be easier for me to go faster and / or to produce more power ( in Zwift and in real)?
Is the weight / set up of a road bike clearly made to enhance performances compare to a MTB or even a very cheap road bike?