Final testing, I got a USB-C socket tester and now I can test if the claimed 3A output is real when using USB-C cables both ends and in a claimed 3A output 3A input tablet.
I compared the Google supplied 3A wall charger, an Anker Powerport5 USB-C with claimed 3A output and a Choetech 6 port with 2 USB-C 3A output and 3 different cables from Anker and Choetech. I also then compared with a USB-C out of the 2.4A output.
- Anker is no slower than the Google charger, about 2.8A, not 3A but note this could be limited by the tablet I was using but that's academic as that is the tablet I'd want charging.
- shorter cables better than longer cables (which we kind of knew).
- 2.4A output ports give about 2.2A so really for USB-C port you gain (0.6/2.2) about 27% faster charging. Useful, but not really necessarily worth lugging a specific larger charger.
I think therefore I'm going to stick what I bought, that if I want to charge lots of devices including my tablet, the Powerport5 USB-C is a good reply, but if I want real compactness, a Powerport2 or 4 isn't that much slower. Porwerport5 means you have the long cable to the wall and then short USB cables on your desk, which is faster charging than a wallwart type with longer USB cables.
Camera auto-focus grrrr.
Powerport 5 "2.4A max" Micro-A to USB-C in short cable gives 2.25A, that is fairly consistent conclusion, that really 2.4A is more like 2.2A.
Powerport 5 USB-C on the USB-C port on a shorter 3ft USB-C both ends cable shows about 2.8A, not the 3A but that could be the tablet not capable of ingesting 3A.
Same as above but with a Choetech USB-C to USB-C cable, about the same Amps.
Choetech USB-C port on Anker cable, similar Amps.
Powerport 5 USB-C using a longer Powerline+ USB-C cable, drops to 2.25A, so if you go with USB-C and a long cable you're losing all of the 3A gain in cable loss, no better than a 2.4A outpu port on a shorter cable.
Choetech USB-C port with Choetech USB-C cable the same 2.8A we see with the cables not so long.
Choetech USB-C on the longer Anker Powerline+ USB-C cable, the same effect of dropping to 2.25A, so same conclusion, longer cables are dumb!
The official charger 2.8A output.
Powerport5 USB-C with the Choetech USB-C cable the same 2.8A we see when not using the longest cable.
Anker didn't fail, no worse apart from its longer cable but that's just physics.