my opinion is sound differences when using different cables are very subtle and mostly related to stage and background noise. personally, i don't mind to spend a bit to get these differences because my experience after long listening sessions is more enjoyable. but always keep proportion. my best cans/iems cost around $350-$700, and my best cables cost around $150. for analog interconnects, i'm DIYing cables using neotech UP-OCC silver and copper solid wires (they are short and rarely moved).
to get different tonality ("signature") i'd better try tip rolling or equalizing, cheaper and more effective.
about 4 cores vs 8 cores (same cores types), i also think i get slightly fuller bass with 8 cores, but it could be bias (i don't think i'd pass a blind test). lower resistance is always welcome (i won't repeat why), specially if driving iems with balanced armatures, but maybe it isn't critical in your case (i own sources with very low output impedance, around 0.1ohm, and many BA iems, so i like to keep cable resistance low; it's a matter of perfectionism, i don't think there will be noticeable sound differences while staying below 400mOhms cables). about their weight, cable 175 4 cores (2.5mm jack, standard length) weights 21.5g, and 8 cores version weights 28g (32g in the case of 4.4mm jack), so not much difference.