My friend and I both with 5900x CPUs in new builds are having the exact same issue.
The strangest part is we find turning settings to max or minimum barely even impacts fps at all it's just the same inconsistent, unstable and low FPS issue which makes Valo almost unplayable. There are lots of 5900x benchmarks online showing Valorant fps in the mid 400s to low 500s. Can pin 400fps easily in OW, can pin 240fps easily in Apex (I limit it to 190 for stability in Apex though) both while streaming. Only game that has the issue is Valorant. Is this a known recent issue that Riot haven't fixed yet? The FPS is so inconsistent that it drops below 100 in some fights and is at low 200s at other times but usually sits high 100s in game which is terrible with this spec level and feels awful with a high refresh rate monitor.
When in game my CPU and GPU and RAM utilisation are all extremely low (below 50%) so no bottleneck that I can see.
Everything is fully updated as far as I can tell.
Tried everything I can find online.
Even followed both of Panjno's tutorials and none of the steps made any noticeable difference in FPS.
Strangely some of my other friends (not on 5900x CPUs) got huge FPS improvements with disabling fullscreen optimisations but no huge benefit for my friend and I for some reason.
I think my friend has the same motherboard as you and mine is just the slightly updated dark hero version so I wonder if perhaps it's an ASUS motherboard or software issue limiting the 5900x specifically in Valo only because those are the two things we all have in common?
Any help is mucho appreciato
===My specs===
AMD Ryzen 9 5900x (stock)
ASUS Strix RTX 3090 White (stock)
G.Skill TridentZ Neo 64GB 3600MHz CL16 (docp oc)
ASUS ROG Crosshair VIII Dark Hero X570