I am somewhat familiar with the Gaia and Garmin ecosystems, but have no experience with carplay.
I advise to spend the $20 and try it. Whether the UI suits you or rubs you the wrong way---you'll only find out by trying to use it.
Gaia should be be fine on your 32GB iPad as long as Gaia supports the iteration of iOS that your iPad runs on. 32GB is just enough memory to store a nice selection of maps, assuming that all other apps and data will be reasonably minimized. The map called Gaia Topo (feet) is a super efficient vector map that can cover huge areas of the country in just a few GBs of storage space.
I think Gaia is fairly intuitive to use, but expect a few moments of frustration while figuring out all the controls and their usefulness.
Gaia does a pretty good job of displaying your location superimposed on top of your choice of available map. That's mainly what I use it for---seeing where I am on a map.
It can record your movement as a track, allowing you to follow your own path in reverse, and can save a track to memory. It allows you to save---and give your own names to--- waypoints. All useful functions.
To my knowledge, Gaia does not 'navigate' for you; It does not provide turn by turn directions. You have to decide, while watching your movement on the map, whether to turn left, right, or go straight.