General Overview-
I have similar experiences with those issues. Im using xl2546k, 6900xt, 5800x3d (everything is stable and is water cooled so very low temps), 0.1% lows at 240 (even in dropship), and yet my game still feels worse than playing on an xbox 360. Its not smooth, full of stutters, prediction errors, and especially bad stutter/prediction errors/no regs right when I get shot. In contrast, all my other games feel great, super smooth, and no stuttering. This includes heavy games like warzone. My internet is also perfectly fine.
Troubleshooting and Solution-
I have tried pretty much everything. Besides the usual updates(chipset, bios, windows, ect.), ddu>clean install drivers, clean windows (10 and 11) install, uninstalling apex/steam then deleting all files and clean installing, and many other things including much simpler trouble shooting. I had the same experience as you when I tried windowed mode but I wanted to find another solution to run fullscreen. I recently did a clean boot and disabled all services that were non-microsoft. When I went to launch the game, steam requested for steam client to be repaired/installed due to it being disabled from services. After steam client installed/updated I launched the game. This for some reason made the game feel like any other game and took away the choppiness along with no regs, stutter, prediction errors, ect.
One thing to note is that every single time I have booted up the game (except for clean boot) the main menu screen with the green flag (it has the words "Apex Legends Hunted" and the "Continue" button right below) has visible stutter. The green "flag" has very fluid movement so it is very noticeable when it stutters. The only time the flag has not stuttered for me upon launching the game was when the steam client repaired itself due to clean boot.
Another weird thing was clean boot changed my fps cap. I use the launch command "+fps_max 240" (no other launch commands) which holds it at 240 perfectly fine. However when I preformed the clean boot I was sitting at 228fps in game. Not due to low performance or anything it seems like it randomly defaulted to this value. The 240fps command line is still present. I'm not sure why this happened but maybe the game is just unstable at 240? But this wouldn't make sense as many pros play at 240 and I don't see them having issues.
I attached a screenshot of what services I specifically disabled when I preformed a clean boot. I google searched all the processes to see if I could find a correlation to issues in apex but found none.
Things to note about the screenshot of the services that I disabled when preforming a clean boot.
First, you might assume that one of the amd services was causing the problems. This is not the case as I recently swapped out my nvidia gpu for an amd gpu but still had the exact same issues on the nvidia gpu. I had also previously tried disabling those amd services and it made no difference.
Second, this screenshot was taken after launching the game and steam client repairing itself. Before launching the game, both "EasyAntiCheat" and "Steam Client Service" maintained the status of "Stopped" but have the status of "Running" in the screenshot because the screenshot was taken after launching the game.
The things I think it could be- I have no idea. My best guess is it has something to do with steam client and the fps cap changing from 240 to randomly 228. Maybe something to do with LGHub.
Try a clean boot and lmk if it makes any difference. I want to play at 240 but I don't want to change anything now that it seems to be working. This is the only time my game has ever run well.
