One of the problems with running neopixels over a long distance is dealing with line capacitance. A 74HCT245 level shifter doesn't have the ability to pull the data line to ground quickly enough. This results in the logic low voltage of your data line being higher that the logic low threshold for the neopixels.
The differential transceivers will work down to 3.3 volts. By powering them off the same point as your first neopixel it ensures that the DATA IN voltage to the neopixel is always the save as VCC. meaning you wont get any higher voltage from your data line getting fed backwards through the neopixel if they are pulling your VCC line down due to its current draw.
I have done some preliminary testing with at least 350 feet of ethernet cable
The Right angle breakout boards are for use with the side lit variant of neopixels. Soldering wires to the copper pads of the tape generally results in the copper pads being torn off with any force on the wire. There is also a spot for soldering on a inrush limiting capacitor if it is at the start of a strip. The trace on the signal line can also be cut to add an inline resistor to reduce ringing.