For value,those are good choices. Poplar is the go to species for most cabinet work when grain doesn't matter. Hard Maple or Walnut are more dent resistant but more expensive. Oak and Ash cost more plus show alot of open grain when painted.

Poplar is often called the Painters wood because of the smooth surface and lack of grain. Birch and maple(softer and harder respectively) also have smooth surfaces, but are more expensive, as a rule, which makes little economic sense when painting.

Using plywood for cabinets is done because plywood is more stable and much less expensive(material and labor) than using wood in board form.

However, using ply for face frames means the edges(showing all the plys) are visible. Very unsightly.

Not sure using maple and cypress together is going to look like. The maple has a much different grain type/pattern than cypress(which is only a little harder than poplar), will take stain differently, and look completely different.

Unless the cypress is the look you want, it will look better using maple ply and maple face frames and staining them.

Or, using birch(or substitute) plywood with cypress veneer and cypress face frames.

Poplar is the go to for paint grade cabinet parts. It is absolutely ok. As for hardness I have discovered discrepancies,some boards are much more dense than others. So, as a cabinet builder these are the proper choices. You could opt for maple or birch on all paint grade. The price will be more but at least you may feel better about it.

Here in Oregon we have poplar farms and they grow the heck out of them. I will say that as a carpenter I do come across some rather fast grown poplar otherwise less dense and lite. I do prefer the more dense poplar to work with. Don't be afraid to tell your cabinet guy what you want, after all its only your $ and you are willing to pay more.

happy remodeling