Since we're talking about an actual circle, I assume we want a circle that stops. (Otherwise, it continues closing until it finally becomes a line on the 9th contraction.)
here's some additional data on the circle.
According to the chart above, the answer OP is probably looking for is 50m.
There may just be coincidences with a lot of people having similar gear. I often see the same stuff because people aim to get the better gear and obviously level 3 gear will be the most benefit to you. The places with higher loot spawns, and better gear tend to have a high percentage of players dropping at so it's not unlikely you'll see a lot of players with that better gear.
As far as I known in my time playing, and from reading forums and threads about loot spawning, there doesn't seem to be any particular weight applied to certain things spawning in different matches.
Common loadouts are ARs with a shotgun or SMG, in my experience, which is why they're so commonly seen. The more powerful guns have less frequency so that also contributes to seeing more SMGs around the place.
Some early threads like these all mention how it's weighted towards certain zones having better loot, and the farther away you are from them, the more RNG is factoring in. In my experience the more isolated places tend to have some things in them, and a variety of gear, but there is the chance nothing/little amounts of things are there.
If you check out various loot spawn guides like this or this, they'll tell you that you're guaranteed better things at places like the Military Base, the School, or the Power Plant to name a few.
Here is an image which shows the general distribution, and as you can see, some places are much more weighted in the amount/quality of loot spawned.
Best Answer
Level 1 absorbs 30% of incoming damage, level 2 absorbs 40%, level 3 absorbs 55%.
This spreadsheet contains a breakdown of the damage in the game whether it be how much damage a particular gun does or how much damage it does to a certain piece of armor and the damage mitigation for each piece in general:
https://docs.google.com/spreadsheets/d/13ZI5GQDbCXl7IlVCVnEA6aZVfC7NFJLBsXPIAGFMNj4/edit#gid=1777964351
I would also recommend heading over to the PUBG subreddit (r/pubattlegrounds) for a lot of other helpful info