Hello,
this topic isn't really covered well in the materials we have so I'm asking here for answers.
Basically the 2 questions are:
1. What is the role of the M1 transistor?
and
2. What is the role of U1 and U2 opamps?

I reckon the M1 is just there to provide a huge input impedance for the mixer stage since it has gain of 1 (checked in the simulation). The opamps I know are in non-inverting mode and I would just expect them to basically delay the signal for a small duration since their gain is 1. I put their output signal in the second picture. Anyways, any perspective and help is welcome.

 

My quick look 2c answer as you seem to have put some effort into it.

M1 likely a phase splitter.

U1, U2: Isolation and buffer amps for the mixer stage.

 

My quick look 2c answer as you seem to have put some effort into it.

M1 likely a phase splitter.

U1, U2: Isolation and buffer amps for the mixer stage.

So U1 and U2 primarily want to stop the local oscillator signal from getting to the baseband port? Also, thank you for answering.