I thought so far that "cache" is part of "RAM"? Or what is the difference? There are two different options available, so there must be some kind of difference, I guess.
RAM is the space in the main memory used by the running processes. Similar to the RAM used in desktops and laptops.
Cached data includes files, images, scripts and other multimedia files stored on your device by a website or application. The data is stored on your devices in a reserved space, so the next time you visit the application or website, the information will be available.
I would like to know if it is totally okay to delete those 2 things (ram + cache) from time to time (and for all applications)? I know that deleting the cache has no negative effect, because sometimes I deleted the cache of applications. But I never deleted data from RAM. And the thing is also that the configuration says "… for ALL applications". So there are applications such as "contacts", "calendar" or other relevant system applications included. I am not sure if you can also clear the RAM / cache of such applications.
No problem if you clear the cache and RAM. In fact, you should do that regularly to keep your phone efficient. Even after clearing the RAM, some processes would restart; So ignore them. Otherwise, it would stop all processes that are not being used at this time.