Oh wow "rare" AMD GPU user at least one that is voicing the issue :)
I don't know about you, but I have had issues with FPS stability since day 1 and read a lot about it -> all went down to two factors:
1. Apex is optimized for Nvidia
2. Apex in general is very bad in terms of optimization (they have had multiple times where they removed effects because they crashed FPS including some of the dive trails :D)
I personally play on 3600X CPU, identical ram, Apex is installed on fast M.2, and 5700XT GPU. Given I have 2k monitor I play on 2k / 1440p resolution all low and my FPS rarely exceeded 200, "stable" 120 max excluding dropship where I regularly got 80-90.
Based on the post I assume you play 1080p or upscale the game?
Also another issue might be windows 11, I am hearing a lot of bad things about it in relation to gaming, need to tweak it a lot to get max performance, in this case I stick with Windows 10 which has also been tuned over time but only thing that really help game vise was network setting optimization.
Otherwise I gave up on stable FPS -> enabled Freesync + Vsync + Radeon anti lag (recently Apex seemed to have adjusted / made game compatible with it) = game now has bigger input lag, at times feel rubber banding but at least I can track people better, shots register more predictably.