Changing output resolution

I used to have a mac with an intel chip which could easily output video from OBS to an external video encoder (LU300s) and change the resolution to output 1920x1080.

Now, I have the M3 MacBook Pro and, despite changing the display resolution from system settings -> display, I can only output the monitor feed from OBS into my encoder at a 4k resolution (there is no option to change the output or to auto deprecate the quality to 1080p). My LU300s encoder does not allow for 4k streams to be transmitted so this is preventing me from using OBS and my encoder to run live streams.

I have gone through tech support with the LU300s company, but the issue is clearly on my MacBook side because I can see that I am outputting in 4k to the encoder even though the resolution is changed in display. Additionally, I know this is a m3 chip issue because I can still use OBS and my encoder from my intel chip MacBook Pro.