The title should be pretty self explanatory.
Dear Larian, I appreciate in principle your design philosophy about how the players are allowed to attempt to kill *any* NPC or creature in the game, even when plot relevant, but "allowed to attempt it" doesn't mean you should make it easy for them.
If we have a meeting with a creature that is supposed to be far too powerful for our level range, let it be so. Don't scale that creature down to our level to accommodate our ego.
Just make it clear that it's a bad idea to even try.
And don't be afraid to put a "level 20" encounter as long as we are not supposed to face it in combat.
Also, as we are on topic: there's absolutely no need to show us the level of every NPCs or monsters we meet just under their name, to begin with.
"Checking before starting a fight if our levels match" is not the feeling that adventuring in D&D is supposed to give.