Vaultwarden keeps an encrypted file local to the device you access it from, like your phone, and if the instance goes down you're still able to access them but not add new ones. This let's you export the file into a replacement instance.

If you ran the install via docker you'd need to set up your folders and the software will do the rest for you, so depending on how you set it up you may already be good.

When you add your download software you tell the arr where it's sending the downloads, say tv/downloading. Then when ever you add your show you pick where you want to add it, say tv/drama/show_name, then the arr will talk to your download client and when the client says the work is done arr will look in tv/download/show_name and it'll move the files for you to tv/drama/show_name.

I've used both podfetch and the project it's based on podgrab. They do well enough but in the end what worked best for me and sounds like what's best for op is audiobookshelf.

Just a few days ago i finally added my podcasts to my Aufiobookshelf instance and i'm kicking myself for waiting so long to do it.

As someone who self hosts things for fun i see no drawback to running my own instance and limiting it to a hand full of people i know. The hardware requirements for a small server are minimal enough most any older laptops laying around could likely handle it. Yes, i can only see communities i've interacted with and you could argue that limits my experience but i'll argue that out allows me to tailor my experiences to my tastes. There are plenty of search options and auto populating softwares that my feed is plenty full enough as is.