For speaker wire:
1) you're looking for solid copper as opposed to the cheaper copper coated aluminium (CCA) or steel (CCS) often sold on Ebay and through less reputable resellers ('tick one' for the Symphony)
2) power loss increases with distance and can be offset somewhat by thickness; so the longer the runs then the thicker the cable required to compensate. Minimum thickness should be 0.75mm2 cross sectional area (CSA). 1.5mm2 is better. The power loss over short distances (<5m) is minimal (aprx 5% for 0.75mm2, 2.5% for 1.5mm2), but grows with distance (10% and 5% respectfully at 10m).
The other effect of cable thickness is in damping. This is how fast the speaker cone can be brought to rest after a note finishes. Thicker cable has better properties in this respect, but this is more a factor with large speakers rather than smaller satellites.
There's no spec for the Symphony cable - it gets marked down in this respect.
3) number of conductors - This is to do with how electrons flow though conductors. It's called 'skin effect' and it describes how lower frequencies travel deeper in the core of each conductor and higher frequencies travel closer to the surface. Cables with hundreds of tiny filaments are okay for high frequency, but the conductors don't work so well for bass. Apparently the optimum balance of surface area to conductor cross section is 42 stand @ 0.75mm2 and 79 strand @ 1.5mm2.
Finally there's whether the cable is oxygen free or not. Any decent Hi-Fi cable will be oxygen free anyway, so it's kind of academic .
Banana plugs
On the backs of wall hung speakers?.... very rarely required.
For stand mount or floorstanding speakers?.... optional.
In the back of AV receivers where all those speaker sockets are crowded together? ..... Oh dear God yes. Life will be so much simpler.
Sub cable:
If you were prepared to spend £20 - which isn't a lot really for a 7.5m sub cable - then you can get something much better specified and a lot easier to conceal around the room.
First, the two cables; RS and Fisual. Neither has a lot of spec. Gold plated connectors look nice, but the few microns of gold flash won't reduce resistance significantly. Bright nickel plating is just as effective at providing corrosion resistance and is arguably a more durable finish, but gold looks nice
Mylar shielding is good at the sort of frequencies used in TV and satellite signals, but useless at audio frequencies. A woven braid shield is far more effective. Two woven braid shields are even better. While on the subject of shielding, budget shielded audio cables are more likely to have a spiral wrap braid because it's easier and cheaper to produce. It's not as effective though because it allows gaps as the cable is flexed.
There's no information about the impedance of the cables or the plugs. Some would argue quite correctly that line level phono sockets don't have a standard for impedance, so the argument goes on that it doesn't matter about cable impedance as a result. The counter argument is that every impedance change between a source and destination device is a potential signal reflection point. Signal reflections are bad. Replacing a cable of unknown specifications with a 75 Ohm lead removes two potential reflection points. But more than this, you're far more likely to be installing something with better build quality and consistent performance where the manufacturer has a set of hard and fast specifications. So you are replacing unknowns with something of tangible quality. If that came with a massive price penalty then you'd be justified in asking if it's worth it. But the fact is that high quality cable isn't expensive. You can often find something with a solid set of specifications at a similar price to the cable that has little or no info. You just need to know to what to look for.
The Fisual cable is cheap and the plugs look durable. Beyond that there's nothing solid in the spec that says anything of value. The Cambridge Audio cable has a little more information, some of it is irrelevant, and I'm not a fan of cables with moulded plugs, but still there's not really enough to justify its price when there are better choices around for similar money.
QED makes 'Performance miniature subwoofer cable' which is good and very thin. It's pricey though at £10 per metre with plugs fitted. There is an alternative, same size, same quality, at less than 1/3rd the price.
** No buying or selling outside of MM **
Good luck
