Not able to find answers and resources regarding JLH headphone amplifier.

I have tried everything, google, ai assistant and diy audio but I am not able to find answers to my question.

My questions,
first
in image 1 output transistor q4 is tied to r6 resistance which is part of constant current with q2.
but
in image 2 two out transistor is directly connected to rails.
what are the pro and cons of each approach.
why to chose one over another ?

second
in image one no constant current source is used with q1 while it is used in image two with q4.
what are the pro and cons of each approach.
why to chose one over another ?

third
i am looking for good resources so that i can learn how to properly bias the transistors and select optimum resistance values.
could someone put towards right direction or guide me how to calculate the current and resistance values for chosen transistors and operating voltage.

any assistance would be appreciated.
thanks and regards.

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