BJT amplifier negative feedback question
You show a emitter follower.  You can think of it as having negative feedback, but that's a little awkward.  It's easier to think of the B-E voltage being roughly constant.  When the load draws more current, it pulls down on E.  That increases the B-E voltage, which causes more C-E current, delivering more to the load.

The net result is that the load sees a low impedance source.  At first approximation (B-E voltage is constant), the output impedance is the impedance the base is being driven with divided by (transistor gain + 1).

Yes, understanding the few basic single-transistor amplifier configurations, how they work, and their general characteristics, is important if you ever want to be good at designing circuits.