When does puppy mania from lack of sleep turn into needed excercise time?

We adopted a puppy from a rescue last month, and she just turned 16 weeks. All we know is tha mom was a border collie mix, and she is an extremely smart dog. I know I've got my work cut out for me, but thanks to these forums I learned about over-stimulation due to lack of sleep. We have to enforce naps with a crate, because she hasn't learned how to calm down enough to nap outside of it. It was a rough first week because she came home with a case of coccidia, but has been cleared and is doing much better.

Now she's starting to get more energy, I know that the need for nap time will start to lessen, but am unsure what that transition will look like. Some sites say a 16 week old puppy only needs 14-16 hrs, some say she still needs 18 hrs. I dont want to force naps if it isn't needed, but it's really hard to figure out if she is getting manic from over-stimulation or she needs more excercise.

Outside of nap time we have a pretty consistent play/train/attempt to hang out and be calm schedule. She learns fast, which leaves me frantically learning new ways of doing things to challenge her brain, because she also gets bored fast. I just don't know how much is over-stimulation when she can somewhat successfully sit/stay for her favorite treat. She just got her last vaccine's, so we are starting to add walks into our day. Any help figuring out that transition, will be greatly appreciated!