I found a solution to iOS 14.6 Podcast app draining my battery and overheating my phone.
Exit Podcasts.
Select Settings.
Scroll down to Podcasts and click on it.
Scroll down to Automatic Downloads.
Turn off "Enable When Following".
(You might also consider turning off Cellular Data" if you don't want Podcasts to use megabytes you pay for.)
(Consider turning on "Block Downloads Over Cellular").
Exit Settings.
Open the Podcast app.
Select Library.
Select Shows.
Choose the first Show.
Click on ... (three dots at upper right).
Choose Settings.
Turn off "Automatic Downloads".
Click Done at upper right.
Click the back arrow at upper left.
Choose the next show, click ..., turn off automatic downloads, click Done, click the back arrow.
Repeat for all your shows.
This will stop the automatic downloads of unwanted shows that are overheating your phone. In addition to turning off automatic downloads, I also turned off notifications to avoid being notified about every new episode for every show.
If any Apple people are reading this, I suggest that you communicate to internal app developers that they should choose default settings that do not overheat the phone, or drain the battery, or overfill the memory, or overuse data.
1) Automatic Downloads should default to off.
2) Background Downloads should default to off.
3) Notifications should default to off.
4) When I go to Settings, Podcasts, and turn off Automatic Downloads, this should turn it off for all shows. I should not have to go to each show individually and turn off Automatic Downloads.