Is it a good Idea to have a lot of wonders on Earth or spread them out? Things like Hyperion Shipyard and the Omega ship I have been putting the same planet, typically Earth. Is it good to keep them together or split them up on different planets?
Wonders give you an increase by percent. Thus it is always a good idea to build a wonder on the best planet.
But the increase is based on the base values of a planet, i.e. when you have two equal planets it doesn't give you any advantage to combine them on one.
What a good planet is, is mainly determined by the planet class (PQ value). But population and the base influence are important, too. Base influence of a home planet is 20, other yellow stars have 10 to 14, and the rest can have 0 to 60 (compare Link).
Furthermore you should be aware of the caps Link . Especially the economic caps often hits you and together with starbases the production cap, too.
Conclusion: it is always a good idea to concentrate influence wonders on earth, unless you are lucky and find one of the seldom high influence stars. Furthermore it is a good thing to combine production and ship quality wonders on a high PQ planet together with shipyards etc (I usually build shipyards only on this single planet). This can be Earth but it is not necessary. Build warships on this planet and constructors on the others. Build the first economic wonder on Earth but spread the others.