Class interval or Standard Deviation are the terms your likely looking for. To have a 24/7 que riots MM has to make a game so ultimately there's no real cap on the range.
In the OG Elo it was 200 points and represented 76 to 24% odds for a class interval gap.
This is why I have beef with Duo que, cuz that its off ranks not MMR and the visible player percentile gap is something like 70% of the player base from a silver 4 at assumed Bronze MMR qued with a G1 at assumed Plat MMR.
We is the variable that impacts MMR raiting gains or loss in relation to MMR gaps. So folks who are expected to lose who lose don't get hit as hard and folks who are expected to win that win make smaller gains. MM is a factor in MMR systems so super dramatic gaps are less likely to happen. Good MMR uses a tighter MMR range for its MM as much as possible.
Sorry, I know this is not a direct answer to your question. The direct answer is No, I don't have any idea on if or what MMR gaps allowed by MMR roughly tend to be because its not a set value and riots MM system information is not provided to let any one know its priority. It seems to be roughly 1-2 divisions at worst for dedicated solo but duoing fucks it all up randomly as does high uncertainty and some Preseason fringe cases.
I also don't have good information on what Riots Positional MM system looks like, Everybody things that got gutted but as far as the information I have seen the only thing removed was positional Rankings/ques. Positional MM was added preseason and Riot Sap magic seems to be a fan. On paper it makes sense to me, thou it would fk up OTP players a bit if they main highly popular roles.
I've asked a few folks for some screen caps of LP slant but all of 1 dude have expressed interest helping with trying to use Slant to look for a pattern in MMR gaps. Oh well.