is the sweet spot always the same for the level of lock?
No let’s say we go with a clock for the directions of the lock. If you pick a lock on the left side of 12 normally the next lock you pick will be on the right side of 12. Normally not all the time.
Exactly where on the 180-degree arc the sweet spot will be, is random for all locks. There is no 'most likely' spot to find it, for any of them. The only thing that differs from novice through master, is the width of the sweet spot.
On novice locks, the sweet spot is about this wide ----> __________________<----
On Master locks, it is about this wide ---->__<----
Plus, the damage done to your pick each time you use it outside the sweet spot, seems to get significantly higher as the locks get more difficult. You can wiggle your pick (don't go there...) a lot on novice without breaking it, but it only takes one or two missed wiggles on master, to break it- unless you have a really light touch. But even then, you'll use a lot more picks to open a master lock, usually.