SteamP2PInfo VS WhereDoThePeersComeFrom

That can't be true because there is an app that does exactly that: https://github.com/tremwil/SteamP2PInfo. It even works in Elden Ring multiplayer

Any (I use for ER)

Try this application. It's really nice because not only does it put them in your recent players list, it also gives you info about their connection so you can at least try to anticipate the laggy bastards.

It's a trustworthy program I promise

Here ya go

Steamp2pnfo on git is pretty nice https://github.com/tremwil/SteamP2PInfo

This behavior is observable in Elden Ring and Dark Souls 3. Both games run smoothly in Windowed and Borderless Mode by default. But as soon I use some applications that add overlay on top of the screen (https://github.com/tremwil/SteamP2PInfo and I even tried to write my own external C application that just said: "TEST" in the middle of the screen) both mentioned games begin to have some sort of weird lag that looks like everything updates slowly. For example if I run next to some vertical objects (pillars) I can see how they a bit "fluctuate" and this cause game feels insanely jerky and not smooth. So I went ahead and forced vsync off in Nvidia Control Panel and tried to play the game normally. Even without Vsync both Elden Ring and Dark Souls 3 are running smoothly with no lags and tearing. But when I run external overlay (either P2pInfo I mentioned above or my own C application) my screen begin to have horrible tearing. I don't know why does it happen but it looks like external overlays breaks something related with how Windows interact with vsync / windowed applications which cause all these issues. It's clearly not overlay program issue. The only common things about these overlay program that they are work only with windowed / borderless mode and draw overlay on top of the game window (not internally like MSI Afterburner for example). So is there any settings or anything I can change to prevent this from happening?

there is a 3rd party tool that lets u check people in your session and their ping

Here’s a tool I built. The docs may not be up to date as I’ve got a private mirror, but it will let you capture the UDP stream and have a look at the packets.