THere isnt much stating the validity of companion planting as a whole. Some things, like garlic deturing aphids is one that I know of thats worked for me, and others. Strong smelling plants (liek herbs) will confuse some pests, instead of honing in on one huge patch of lettuce. Most of them are small groupings (say tomatoes, basil, oragano, carrots).

What you are thinking of is reminicent of FOOD FOREST gardening, or a PLANT COMMUNITY. These are larger groups that mimic the plants natural habitat. You can customize these by switching plants that do similar things (nitrogen fixers, nutrient accumulators etc) that you like.

Im going to have to assume you have a decent sized yard. Youll want to use the trees you mentioned as your center pieces of small communities, into a larger forest garden. THis gets too long to fully explain ( I highly suggest you read material on permaculture, which seems to be exactly what you need ). I suggest a book called "gaias garden" by Toby Hemenway ( the best book for making the concepts more "pallitable".

Only real companion planting I do is catnip, and its mainly because pollinators really love those flowers.

Yeah, I wasn't thinking of anything overly complex at this point.

Just some things like garlic, comfrey, nasturtiums, and clover. Just to attract the right kind of bugs and repel others.

Dirty little secret time, if you really want to attract the best pollinators, just designate part of your lawn as a "pollinator attraction zone" and just stop mowing it. Let the grass and the wildflowers grow.

Local native flowers will attract pollinators the best, because its what they evolved to use. Imported plants like catnip work, but local stuff works better. And best part is, local stuff is free, you just have to stop chopping it down as weeds. =)