Switch from HSA to PPO plan

I’m currently on a high deductible HSA plan, and I’m considering switching to a PPO plan, but I’m not sure it makes the most sense since we don’t hit our deductible with the HSA, but still spend around 4k a year on medical bills.

My son has epilepsy and ADHD, so on top of his constant doctors appointments, medications, and therapies for his ADHD, we also have an overnight EEG that we’ll need to schedule next year to see how his seizure activity is.

Looking at our employee benefits, monthly premium is about the same. The PPO is $3000 per family, with a max out of pocket of $6500. Current HSA is $5,050 with a $6,150 max. It says under in-patient hospital that the PPO is 20% after deductible, but what exactly does that mean? I’m terrible at understanding insurance, so I could really appreciate someone could explain it like I’m 5.