Nice module, I did had some issues because the PIC wasn't programmed with the right code. But the seller (Thomas) corrected it right-a-way. It works as expected on my Skoda Symphony radio. nice signal with no distribution at all. Documentation a bit low, but you can build it with some googling and very close look on the pictures.
The NanoPB is based on the 328PB -- a more capable 328P. There are 2 extra pins on the board, so it generally won't be a drop-in replacement for a regular Nano. As Tomas says, if you like to solder or want learn to solder SMT, then buy the kit. I bought one and had difficulty soldering the CP2102 IC -- it's a QFN package and requires a practiced hand to solder. I would recommend this board and I would recommend buying it assembled.
The board design is good and the provided parts sheet made for quick assembly. As expected the board performed well. A design I have using 2 serial ports can now be made with both as hardware ports.
regarding cp2102 I was thinking about option with this chip soldered, but I just do not have time to make it, also when I solder this chip I can solder all components, cose it take 2/3 of time as you say. But you chalange your self, made it and now you can say you can do it in your projects!
I will fix info about drop in replacement, I was talking about breadboard, this is how I use my NANOs.