Rocket Engine Design Question

Back in freshman physics the large lecture
hall was filled to direct students to the correct
curriculum. One class was the old mass thrust
theory. If you could not follow the theory you
were directed to a non-physics department.

I still wonder to this day. I believed it was more
complicated than stated. There was a function
of rocket mass change with time. And a constant
fuel mass burning giving thrust. A fuel mass velocity
equates the theory. Assuming a constant throttle.

My question was the true efficiency of fuel mass
to thrust. The internal chamber structure is my
question. How would a flat plate engine design
differ from a the chamber? Begging the question,
how do chamber designs converge to the most
efficient?

I figure that maybe the hottest engine is the most
efficient. Making the idea that a thermal defect
exists. This is energy radiated not effecting
thrust. This is of course small compared
to chemical thrust. But it does introduce the
concept of chamber internal dynamics.
How would a straight tube chamber differ
from the normal cylinder with nozzle?
And the exact location of the burn in the chamber
be calculated?