Really for me it comes down to it being outdoors. I need the weatherproofing you get by soldering and heat-shrinking. A wire nut can hold water leading to corrosion or worse a short between wires if they are touch and wet.
Depends on the wattage of each pixel. The 100-pixel distance is usually for the 12v bullet nodes. After 100 pixels you usually get too much of a voltage drop when everything is all white.
You might also look at
https://www.amazon.com/dp/B01DYPY0E4?psc=1
I am thinking I like these better since I can do them individually and not all tied to a single location.
I love my pixlite (have a pixlite4). The only drawback to the pixlite is you have to use their program to configure the outputs and the way the program works is it searches your network for an controller. So it does not see it behind the pi running fpp. So I have to take down my control box...
Thing with even the 0.7W pixels is where you are at it will not be a big deal. True.. they make more heat but that won't matter in Washington. Yes they are not 'as' efficient but who cares to some extent =p You will not notice any brightness/color difference.
And he does ship pretty fast...