In pretty much every case where I'm searching for something with a search bar, I prefer the list of results getting updated as I type. Why? It's simply faster.
On Spotify for example, click "search" start typing until I see the band I want in the "top result", press the down arrow, press enter.
If I had to press enter and wait for the whole list of results to load, that would take much longer.
For me the experience fall apart at the "press the down arrow" part.
I took a screenshot of a typical google search session [1] with the search suggestion appearing below the system's native dropdown. For any field where I use the IME, it's the IME that wins, and the dropdown in the background is just distraction [2].
This is the easiest case to reproduce on a blank site, but it's the same for search box where I have autocomplete values (which is a more common problem I think ?); the autocomplete popup will take precedence on any element displayed in reaction to the keyboard, and a "press down arrow" will go to the autocomplete, and not the site's dynamic dropdown.
[2] The other "best" case is when a result is actually relevant, but I can't see it because it's hidden, or it changes/disappears when I dismiss the native popover because the action counted as a focus change or a keyboard event.
Ah, I guess my experience is different. I don't get that "system" autocomplete on Google or anything else. So, i just use the one that the website gives me.
On Spotify for example, click "search" start typing until I see the band I want in the "top result", press the down arrow, press enter.
If I had to press enter and wait for the whole list of results to load, that would take much longer.