I like the big chunky USB connectors. These microUSB connectors are crap, they might be rated for more insertion cycles, but they break easier than any other USB connectors and are the most anoying kind of USB connector to plug in with your eyes closed. The previous miniUSB was pretty standard, more robust and easier to plug in while not really being all that much bigger.
I don't have any photos of my DIY power splitter, but what i basically did was solder 3 troughhole SMA connectors together into a star shape with the center pins pointing together. I soldered 0402 size resistors (I think you need 16.7 Ohm each for 50 Ohm at the port) from each SMA together into a common summing point in the middle. The small SMD resistors behave reasonably well a high frequency due to there small parasitics and flat straight construction. To finish it off i wrapped the whole thing in metal tape so that the resistors are completely shielded inside. Soldering those tiny resistors in mid air like that can be a bit annoying but you can throw one of these together in 10 minutes out of parts you likely have laying around.
Here is an example of a similar one that someone else built:
http://www.simonsdialogs.com/2014/12/resistive-power-splitter-trying-out-a-low-cost-construction/It also worked perfectly good to 3 GHz, but again no measurements beyond to see where the limits really are.
Im guessing with careful controlled impedance PCB design and keeping connections short you could build one of these to perform nicely even past 10GHz. Resistors are dirt cheep but the PCB and the connectors could get expensive in a hurry for such high frequencies.