Cooling them converts much of the starch into resistant starch, which not only reduces insulin spikes, but it helps feed the microbiome. No need for freezing. Also, you can reheat them, but do so slowly to avoid breaking the molecular bonds that characterize resistant starches. Maybe microwave them for 20 seconds, wait 30-60 seconds, and repeat until sufficiently warm - as opposed to sticking them in for 90-120 seconds to reheat quickly.
When I reheat them, it’s often on the stovetop (for potatoes). One of my favorite ways of making homemade hash browns is to throw an extra potato or two for baking, then refrigerate instead of eating right away. Use those potatoes, diced, for my hash browns. So good and now better for me because of the resistant starches.