Hey Katz and all. How am I going to know the difference between a well-fit bike and just getting used to riding again?

Say, in the beginning as I will be, I get aches, hands, arms or back.. How do I know it's just an adjustment period versus the bike being ill-fit for me?

Not sure what you mean by upper level riding
I guess I mean racing. competing.

the bike I'm ordering won't have the skinny tires. I went between the both, I think they call it. wouldn't mine also be a hybrid if it can go both places? road and off road?