Charging pattern of iPad 8th Gen to keep up good battery health

Yes. You can use your iPad whilst it is charging.

Rapid discharge how? Normal use will pose no hazard to the battery. Your iPad will optimally charge its battery whilst it is connected to its Power Adapter. The only hard and fast rule is to never leave the iPad in a discharged state - as doing so can cause irreversible damage to the Li-ion battery.

Having an iPad continuously powered for extended periods is not an issue - as this is common practice in POS (Point of Sale) and Kiosk applications.

iPad will optimally manage battery charging - and may automatically change its charging strategy by reducing the maximum battery charge level to about 80% of maximum capacity. This strategy is intended to extend the life of the battery by reducing chemical ageing that occurs when the battery is continuously maintained 100% charge. When a “normal” charge/discharge pattern is resumed, charge to full capacity is restored.

More information about iPad’s battery management can be found here:

About iPad and iPhone Charge Management Feature – Apple Support

That’s hardly a “rapid” discharge. Discharging to 20%, 50%, 70% prior to recharge will no difference. Unless being left in a very low charge state, when damage can occur to the battery, the total number of battery charging cycles that the battery can sustain is broadly the same.

For every full charge cycle, the total amount of charge that the battery can accept reduces by a tiny amount. For iPad, the battery is quoted by Apple as being designed to retain 80% of initial battery capacity after 1000 full recharge cycles - a full charge cycle being any combination of charging that amounts to 100%. So, charging by 50%, 30% and 20% amounts to one full cycle.