This is where the “electricity in wires == water in pipes” thing that I have in my head breaks down a bit. It isn’t directional. As long as you keep the polarities straight, you can connect power anywhere you need to along a run.
The Pixelblaze can be located pretty much anywhere, although you need to keep the data line from the PB to the first pixel fairly short. I’d put it where it’s protected and convenient, wire as necessary and try it out. If it works great! If not, you can run a much longer data line by using either the Pixelblaze output expander (I’ve run upwards of 35 feet between PB and strip that way) or a buffer chip, as described in this thread