Hi Pecan,
my PC is an Intel i7 8700K 3,7 GHz, a very fast machine.
As I said, those "hiccups" started at some point, I would say between last Spring and Summer, sadly I can't say for sure from which Nightly Build

But everything was fine and smooth before that point !
The clangd client is already disabled.
As for the Browser Tracker, I was suggested here to disable it, by another user who experienced slowdowns by it on startup (but it was not responsible for the hiccups while typing).
As for the Thread Search (another thing which was suggested here) I disabled it but I don't think that helped with the hiccups.
I tired to disable the Code Completion, but it was NOT the culprit.
Those little hiccups are noticeable in particular while moving the cursor thru the text.
As I said, I think the culprit is the plugin responsible for showing those two choosers in the top bar, with all functions defined in the current code. But I don't know which plugin it is, so I cannot try disabling it...