I have experimented with DIY cables big-time over the last few years, moving from coax to weird concoctions to shared earth between interconnects and finally to foils
for me, within my system, foils wipe the floor with all of them - interconnect side by side configuration, with speaker cable sandwiched parallel. Occasionally i take the interconnects to my friendly local dealer to compare to commercial options, and we stop at around £1000, with mine still prefered. Mine cost approx £8 for 1m pair interconnect
I also played around with phono plugs, and heard no real benefit from the top Eichmann bullets vs £1-each amazon basics - this turned out to be my biggest benefit, though, as i figured that solder might be both common to both plugs and also a limiting factor, so i designed & 3d-printed my own phono plugs, which 'formed' the copper foils into the live pin and return path, thus removing the need for solder, and this was better than any soldered plug or contact-fit i ever used
Because the foil is so cheap it was no issue to create the same cable with different widths - mundorf comes in various sizes, but i found that shaving the foil to a 9mm width for interconnects was best, although i suspect this is system dependent . I am still playing with the best speaker width
for anyone really interesting in trying out some designs, i strongly recommend the allan wright cable cookbook, if you can find one - i got mine late in the day, by which point my designs were pretty close to his best-in-class designs (i think i got lucky there, as i am no electrical engineer!), but there were some really good tips in the pages (brasso the copper before sealing with kapton, for example) and also some nice technical explanations of why they foils can perform so well.