You can see error rates very easily with certain switches or NICs. Ive left switches on for months at a time and so any error in this period will be logged. I bet everyone on here switches will all say zero errors and collisions too if theirs is a hard wired system unless it is defective in some way. So i don't buy the cable construction leads to attenuation leads to errors which leads to lower sound quality. Network standards for what 99% of people on here will be using will specifying error free transmission for distances probably 10x what people have in their homes. Ive run unshielded cat6 for over 60m for many years in not ideal conditions including in proximity of other cabling and never seen a reported network error, ever.
As for solid vs stranded, solid is for permanent runs, ie keystone terminated and others permanent terminations, stranded is more flexible for patch cables. You can easily build solid patch cables, albeit not so easily to terminate in RJ45's and cable cost will be penny's difference but you may end up with a more brittle cable if its regularly re-routed. I've never needed to use cat 7 so don't know the construction, but I'm not expecting the uses of solid vs stranded to be any different, but happy for someone to enlighten me.
As for screening on cat 5, cat 6 etc. its not part if the standard. So cat 6 is not better screened than cat 5 unless you specify it - you are just as likely to have screened and or shielded cat5 than you are to find with cat6. Granted, some manufacturers put better separation between twisted pairs say with a back bone, but thats their choice of construction as a way of reducing crosstalk but some cables meet standard without. Cat7 is a bit different as this standard is so tough, screened / shielded is the norm needed to meet the standard, but if your just putting 100Mbs or 1Gb over it, cat 7 is way over kill and has other undesirable side effects that actually make cat5e/6 a better choice in many situations.
So not a simple case of higher spec = better as opposite can be true, more a case as of finding the right cable for the job.