The issue only happens with FF14 on my PC, so I'm not really sure if it's not tied to the game (hence why I'm posting this here first before going to AMD support).

I already went back to WHQL drivers for my GPU, since I was running newer ones. Nothing changed. Tried running the game at fullscreen (I usually play on borderless windowed), but it's still the same. Apart from antivirus, Razer Synapse and Lightshot, there's nothing running in background.
Tried changing all settings to the lowest of the low and changed resolution to 720p, the framedrop still happens.

Thanks for your response though, I think I'll reinstall Windows and see if it resolves my problem.