A Couple Wire Questions...

[EQ3282]

Short and sweet: Just moved in to a new place that has a pre-wired for surround basement. The speaker wire into the viewing room is connected from speaker wire outlet boxes where the receiver goes (so wire will be connected from the receiver to these junction boxes through a +/- hole in said outlet, then goes from there to speakers). Here are my questions:

1 - The wire coming out of these boxes have a copper and silver conductor. Thoughts on this? Better, worse, or the same as copper/copper? Any issue if I use copper/copper to connect from receiver to boxes (obviously maintaining polarity)?

2 - I was using/have 14 gauge copper/copper wire. The wire in the basement looks to be a smaller gauge (possibly 16, but more likely 18 gauge). Any issue with that combination if I don't buy new wire? Is there anything I can use to measure to find out the exact gauge?

3 - I have 8 ohm speakers/receiver. Looks like IF that wire is 18 AWG, 32 feet is about the max distance to work in. I'd say the longest distance (receiver to junction outlet to speaker) is probably around 20 to 25 feet (no more than 30). I guess I should be good, so not really a question here. Just thinking out loud to see if anyone has input on this reasoning.

Will probably have another question or two, but this is good for now. Thanks in advance!