handling of picture compression

Hey guys

i have a older website project with a lot of blogposts and subsites.
In every blogposts are pictures and/or galleries used, which make the project itself pretty big in terms of storage space, backups and so on.
Also the site loads partially too long in my opinion.
The website is localsbodensee.de
It was played around with the perfomance picture settings in the past a lot and i lost a little bit the overview over the behavior of these settings and the folders created. So i need a little help to understand these features correctly.

At the moment image compression 80% is active (see attachement).
when i look at the media folders i see a "compressed" folder which was created because of this, i guess?
But there are also subfolders for tablet, phone, etc...
When are they getting created?
and are all of these folders getting deleted automatically, when i disable the performance folders?

My goal is to clean up unneeded media folders and to set the settings correctly and sensibly for such an image-heavy project.
In the end i think i want to use webp.

Of course, you can have website access to get an overview in detail, if needed.

Please help me and save me from destroying the website! :D

BR, Sebastian

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