The problem ordering the wire from Spruce is that was what I did 4 months ago. That is when I got the white core wire. I suppose you could specify that you want solid rubber “no white core”.
16’ will do the job.
Plug wire lengths;
19.5”, 20.5”, 21.5”, 22.5”, 25.5”, 26”, 26.5”, 27.5”
These lengths will give you about 1.5” for later trimming. The “extra” isn’t a problem in use.