You need RCA to 1/4" converters for the speakers that take 1/4" and you need RCA to XLR for the speakers that take XLR. In fact, you should have a bunch of those anyway, cause you never know when you’ll need them.
And if you have an Audio8 you never need to bring your mixer anywhere, especially if you are mixing internally.
Depends on whether you want to run stereo or not. If the speakers have an XLR in and a out/through, I would use the top cable, then connect the two speakers with an XLR cable. A system like this won’t really sound any better by being run in stereo, imho.
if you wanted stereo, you’d have to run the Left output of the soundcard to one speaker, and the Right output to the other speaker. it’s pointless to run stereo on one speaker.
Yup! if you want to run stereo use your second option of the two you’ve shown and run one xlr to each speaker. I only suggested the mono setup because, except for certain types of music the stereo effect is often lost on a two speaker system in a small area. Either way will work just fine, it’s kind of up to you if you want to run stereo or not. If they’re cheap enough buy both cables and try it both ways to see what you prefer. I have been surprised to find that a mono setup often sounds better than stereo in less than ideal situations, so it’s worth checking out both options.