How can I prevent iPad 11th gen from overheating?

If your iPad is overheating, try reducing the screen brightness (20-40% being adequate when used indoors). When used outdoors, or in very bright ambient lighting conditions, the iPad may increase its screen brightness to compensate - leading to increased heating of the iPad.

If the iPad is in a fitted case, remove the case - as this will improve passive cooling.

Otherwise, if your iPad is not operating as expected, try a forced-restart - as this will often clear an isolated software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

If the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:

How to back up your iPhone, iPad, and iPod touch - Apple Support

When you are happy to proceed, you can perform the reset from iPad settings:

Settings > General > Transfer or Reset iPad > Reset > Reset All Settings

If the problem still doesn’t clear, the next step is to reset the iPad to factory settings:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

If you are unable to resolve the problem , you would be well advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad - and you can explore your available options:

Genius Bar Reservation and Apple Support Options - Apple

I use my ipad at full brightness as i regularly take it out in bright environment and the 500 nits is just drains my battery a lot. I know I could just turn on adaptive brightness but even then in dark environment it goes down to the point where I can barely see the display.

Given your clarification, your iPad is working exactly as expected. Using the iPad at very high brightness will create a lot of heat - and rapidly drain the battery.

Apple always quotes battery life as "up to". Testing conditions will be using a range of non CPU-intensive tasks, with the screen brightness being adequate for indoor ambient lighting conditions. CPU-intensive tasks and high screen brightness will shorten battery life between recharges.

As for using your iPad in low-light conditions, if the screen is too dim, increase the screen brightness slightly in iPad settings. This adjustment will re-calibrate (and remember) the auto-brightness adjustment; similarly, if the screen is too bright, adjust the brightness down.

I am finding that "just browsing" is no longer always a light task. I am finding more and more sites, especially selling sites like Amazon, using massive amounts of energy even if left open in the background. Sites with a lot of embedded videos—like ads—can run up the temps as well as reducing runtime between charges.

What browser are you using? Chrome seems to "phone home" a lot and that ups the device's workload.