If you are going with only a few types of plants I would do all fast growing plants. They will clean the water faster, and create a lot of oxygen.
Floating plants are a very helpful in Walstad tanks. You could find a work around if you really don't want them- like adding pothos to grow out the top instead. Floating plants are the best at removing nitrites and excess nutrients from the water column and do a lot to keep algae at bay. If you're struggling with algae I'd add some floating plants. Many of them are invasive plants, meaning many states will not allow you to sell them, but the ones below should be available in most places.
These are the big gorgeous plants that get all the complements. Make sure you've got enough of your meat and potatoes foundation of fast growing plants and then pepper these guys in. These are where it really gets fun.