How to Correct Aspect Ratio When Recording On Widescreen

So I'm brand new to editing video and I absolutely love premier pro. Its still pretty daunting but im learning. I am a brand new content creator for New World and various other games and just hit 1k subs so i really want to up my youtube and editing game 😉 My problem... I have a nice gaming widescreen monitor with a res of 2560x1080. I use OBS to record and if i need to edit anything, i use premier. There are about 1 million different places/ways to change resolution or aspect ratio. The display settings in windows, the nvidia control panel, the in game res, the obs canvas and output res and of course, premiers various resolution settings. Someone please steer me in the right direction lol, theres just too many options. Im currently using 2560x1080 windows, in game and in obs and the recordings look fantastic! The only issue is, i can't make an ending screen in youtube because i get the message "unsupported aspect ratio" it needs to be 16:9. I changed OBS canvas AND output resolution to 1920x1080 and now my recordings are cropped and it cuts off the side of my game, my inventory.. etc. I have checked online and some youtube videos on how to fix this and i cant seem to get it right. any suggestions? Thank you so much!