As far as high impedence (1/4") cables go...XLR (low impedence) cables are different. No high end roll off ...
The type of connector on a cable has little or no influence on the impedance of the cable. Just because it's got a 1/4" jack on the end doesn't automatically mean it's "high impedance" or that it has high capacitance.
Mic cables (XLR) DO have high end roll off, let me first assure you of that. ALL cables have a frequency response range, there's simply no escaping it. The difference comes down to the quality of the cable itself. Since instrument cables are often a neglected part of a rig, this manifests itself as the notion that instrument cables suck tone - which doesn't have to be the case if you take care when purchasing.
However, what you are saying does have some basis in fact. This is because of the high output impedance of guitars and basses. The low pass filter formed by the output impedance of the instrument and the parallel capacitance of the cable is what causes the high end roll off. Use the same cable with a lower output impedance source (for eg; active instead of passive) and the effect will be reduced.
You can make instrument cables out of microphone cables without cause for concern. You could go the other way too, but usually instrument cables only have two conductors while balanced mic cables require three.
Generally, cables with characteristic impedances are used in telecommunications and video systems. (50 ohm and 75 ohm are the common standards.) However, analogue audio cables are usually
not impedance matched - there's simply no need. Ensure the source has a low impedance, the destination has a high impedance, and the cable in between only needs to be relatively low capacitance and you'll be fine.
gold tip connections are good
yes they are, but they're only as good as the connection they are mated to. Given in most basses, FX and amps these are cheap nickel plated crud, then the benefit of gold tips is significantly reduced. Also, the ground connection is just as important as the tip, and yet it misses out of the gold plating in a lot of cables that I see.