That circuit is not directly useful for BALANCED microphones because it is unbalanced input.
You could put a transformer in front to convert balanced to unbalanced.
If you use a transformer, now you can also convert impedance from very low 150 ohms to some higher value which may be more suitable for low-noise amplification.
> Why in that semiconductors datasheets appears only the ...NF (Noise Figure)
If you can chose ANY source impedance, you pick the impedance which gives the best NF.
> habitual Noise Voltage Density
In transistors, total noise is BOTH voltage noise and Current noise.
Noise Figure combines both noise values, but only at the specified source impedance.
> DMMT 3906 Very very cheap
This is a dual 2N3906, one of the most popular small transistors on the planet. 2N3906 data
Page 4 shows noise curves. Noise may rise below 1KHz, but is fairly flat 1KHz-20KHz, which is what matters in audio.
The top-left chart shows best NF is for 2K source with 100uA of current in the transistor.
The top-right chart shows that for 100uA, the NF at 1KHz is low from 1K to 4K source impedance.
Therefore with a transformer, we would select a 150:2K ratio and 100uA current.
But good transformers are expensive. For transformerless operation from 150 ohm microphones, the top-right chart shows that the best NF is 3.5dB (and 1mA current).
3.5dB NF is good but not very-good.
The 2N3906 is a "small" transistor. When (no transformer) source impedance is as low as 150 ohms, we need a bigger device.
The SSM2220 plan you posted shows 4mA in Q2 or 2mA in each half of Q1. This is typical for best noise from 150 ohm sources.
SSM 2220, MAT02 MAT03 LM394 are the "good" devices for transformerless microphone amps. These have larger junctions with high gain, and are tightly specified for noise and match. They are expensive, demand is small, they can be hard to get.
Many inexpensive but good microphone amps use larger "switch" transistors. They are not specified for low noise, they are not matched, but experience says that in the right conditions, 99 out of 100 will be very low noise.
To handle Balanced inputs correctly you usually want more than one op-amp.
THAT Corp, TI, and others put low-noise transistors and all the op-amps and connections on a single chip. PGA2500, THAT 1510/1512, and others. You will probably have to get these from Farnell or other large international distributors.
> DMMT 3906 Very very cheap
Just for thinking: if one '3906 at 100uA has good NF for 2K source, then thirteen '3906 in parallel would be good for 150 ohm source. Total current would be 1.3mA, similar to best 150 ohm conditions for the devices rated for low 150 noise. The cost could be near 5 dollars, very affordable; but thirteen very-small 6-leg SMT devices is too many for me to solder (your eyes and hands may be better).
Finally: low-low-low-noise is NOT the biggest feature of a mike amp. I have made many recordings, small classical, even children's choir, with electronic NF above 5db. In most rooms, the room-noise exceeds the mike noise.
Also modern affordable Condenser mikes have high output levels which makes the "preamp" noise insignificant. (The real preamp is inside the microphone; our box does not have to be super-good as with dynamic or ribbon mikes.)