Examine this circuit; each of the diffpairs has gain of 8X at low frequencies; but their F3dB (45 degree point) are not consistent; why?

And Q7/8 do not have gain of 8X. Why?

Also notice the leftmost diffpair has no source resistor, thus CMiller can be infinite but the SPICE source handles the input current (Ibase, Cob) just fine; on the other hand, the 3 right circuits include Rin, and that R along with Cmiller impacts the circuit bandwidth.

Examine the circuits below. Each of the three differential pairs on the left have differential gain of 4X at low frequencies. Yet their F3dB (45 degree point) are not the same: why?

^{simulate this circuit – Schematic created using CircuitLab}

And Q7/Q8 - same topology as what you propose - does not have a gain of 8x. It in fact has gain < 1x. Why?

Also notice the leftmost diffpair has no source resistor, thus CMiller can be infinite but the SPICE source handles the input current (Ibase, Cob) just fine; on the other hand, the 3 right circuits include Rin, and that R along with Cmiller impacts the circuit bandwidth.

Examine this circuit; each of the diffpairs has gain of 8X at low frequencies; but their F3dB (45 degree point) are not consistent; why?

And Q7/8 do not have gain of 8X. Why?

Examine this circuit; each of the diffpairs has gain of 8X at low frequencies; but their F3dB (45 degree point) are not consistent; why?

And Q7/8 do not have gain of 8X. Why?

Also notice the leftmost diffpair has no source resistor, thus CMiller can be infinite but the SPICE source handles the input current (Ibase, Cob) just fine; on the other hand, the 3 right circuits include Rin, and that R along with Cmiller impacts the circuit bandwidth.