In my working experience I have come across a Suzuki Alto 1000cc which had acceptable system pressures, new compressor, new condenser, new evaporator, new drier, new TXV,
the TXV was some off brand chinese part which was causing the evaporator not to flood correctly, it would freeze up the lower part of the matrix then stall, then suddenly flood the coil which caused extremely poor performance. I bought a genuine Denso expansion valve and replaced it - That car's A/C was back to perfect working order. When an expansion valve fluctuates - you will want to kill yourself because the gauges etc wont make sense.
btw - having super low return line pressure is also bad as it can cause the compressor to fail from lack of oil.
Here in Houston I have replaced quite a few W124, W140 and R129 evaporators (they are known to be faulty from the factory) - each car takes more than 12 hours to do that job. Chinese/taiwanese unbranded quality is terrible, they never perform good and seem to be cast from junk, their joints are also very sloppy.
A good branded part (even made in China) is acceptable and that is what usually I install back, the TXV is sourced from a MB dealership as it is "geprufte qualitat" or "proven quality"
There is a big difference between a car brand certified part and its similar part. e.g. in a MB one of the OE TXV is made by BEHR, you can also buy it aftermarket - both look the same except one has a MB star and a part no. while the other has its manufacturer part no. the part with the star and MB part no. is actually built to MB standard and tested then delivered (think of it as a rudimentary calibration certificate) the other part is made similar but not to exact spec - usually done to save costs as a lesser amount of testing is done on it.
Japanese parts are also similar.