ICs that drive the LEDS in unused nodes consume a small amount of current even in the off condition. Unused nodes would also need to be defined in the software to insure they remain off.
First programmed setup for me will be Dec. 2020 and I intend to cut to length. Leftovers will be kept for future repairs or to combine them into another strip. In my opinion it is better to trim to length; bit more power efficient, bit less complex network.
I'll be cutting them to length to form a matrix. The plan is 60 x 1m strips of 60 LEDs/m. Positive rail on one end, negative at the other. This will make the current path the same length for all pixels, and keep the +/- wiring separate within the module.