It would appear some folks responded without reading your post!
Anyway, you really should sight-in the firearm yourself.
How a firearm is held can influence the point of impact. And that’s an individual matter.
There also seem to be variances in how folks actually view the sights – though I really don’t know why since there’s really only one correct way to view them.
25 yards from a benchrest is how I sight a handgun in. But that’s a personal decision – there’s no one “right” answer.
Also, you will probably want to start closer just to make sure you’re getting your bullets on the target to begin with. Then make any preliminary adjustments and move the target further away till you get to 25 yards.
Incidentally, don’t let the firearm touch anything hard when you fire it from the bench since this will alter the point of impact.
For me, getting a 5 round group centered tightly on or around the point I want the bullets to strike is adequate. Keep going until you get that - and then you can stop. The actual size of that group will vary depending on the capabilities of the ammunition, firearm, and shooter.
Note that varying ammunition can change the point of impact – esp. if there’s significant differences in bullet weight or velocity. Thus you should sight in with the particular ammo you plan on using.
As has already been mentioned, you’ll actually just be able to adjust the sights for windage. The only realistic way to compensate for elevation problems with fixed nitesights is by trying different ammo.