1. you have to look for spoons that run at the speeds you intend to run at...... If you're running harnesses at 1.5, an NK28 isn't going to work. But to answer your question yes, spoons can be run with other baits. The need to be the right spoons though.
2. at slower speeds, I've had luck with Michigan Stinger scorpions in confusion, perch patterns, blueberry muffin, and chrome blues....... at slightly higher speeds, super slims work in the same colors. This year I've mixed in some Hybrid lures walleye spoons, and am liking them so far. hybridlures.simdif.com Nick is a very nice guy and puts out a good product.
3. I don't tip them. These are pretty light spoons. Not to say that it wouldn't work, just that I have never experimented......... with worms.

For whatever reason, I do better with these small spoons behind wire divers.....

I'm not pounding fish this year...... struggling like a bunch of others...... but these spoons have produced in prior years.