As for whether or not Dak is "elite", it might help if everybody is on the same page as far as what that actually means:
ELITE: a select group that is superior in terms of ability or qualities to the rest of a group or society:
So what does that mean in terms of NFL quarterbacks? I realize it is arbitrary but there are 32 starting QB's in the NFL and 32 backups. If half the teams were developing a quarterback then that is another 16 for a total of 80 quarterbacks in a season.
If we say that 10% of the quarterbacks are elite then we are talking about 8 of them. If it's 5% then we are talking about 4 quarterbacks. I am going to compromise and say that 6 QB's playing in the NFL are elite.
Well, if I start off with a combination of passer ratings and winning percentage, then it' going to look like I set the whole thing up in favor of Dak.
That's because Dak is 6th among all active quarterbacks in passer rating. He's also 6th in winning percentage.
Of course, playoff record is also high consideration. But this also presents some problems.
First of all, what is a better playoff record 2-2 or 2-4? The percentage is better with 2-2 but 2-4 implies that the QB was able to lead his team to a couple additional playoffs.
If I look at the playoffs winning percentage then my "elite" QB's include Jimmy Garoppolo and Russell Wilson. If I look at QB playoffs passer ratings it looks believable for the most part, although it seems a little dated when it includes Aaron Rodgers and Russell Wilson. Some benefited more than others because the team's defense was elite. Any statistical method used is going to devalue Lamar Jackson's unique set of skills.
In the end, the whole question of "elite" status comes down to individual perception, there really isn't a comprehensive formula to determine this. Even if there was, the variables used would be too numerous. The question itself will never provide an answer, only endless, pointless debate.