Help me understand filters

Hello good people!

I need some help to better undestand how filters work. So, what I have now is a general category which is applied to all posts and then I use something like

filters:
  category:
    - Posts

for the search and archives plugin etc.

It works but if a post is saved but not yet published (like a "draft") it will show up on the list when it shouldn't. The same goes for the recent posts list.

In addition to that, I tried using

    filters:
        - @taxonomy: [tag]

just to test the search but then it comes back with zero results, even when I search for a specific, known tag. Maybe I'm missing something.

I was wondering if it's possible to eliminate the need for a category filter and instead use something that includes only published posts. I know about the published: true header but I don't know how to apply it in a plugin config or in Twig.

The whole thing with the taxonomy and tag and all that stuff is a headache.
I managed to make search work by just letting it empty. If i try to add a category,it wont work. Makes sense (ironic tense)

and by empty I mean I had to MANUALLY edit the YAML file of seach and replace/add this:
ffilters:
category:

• '@none'

Through the ACP it wont edit the file correctly and wont accept or save that parameter.I had read some topics that some plugins wont save a correct configuration.