Jumping in here because I totally feel your pain with that fan noise. Honestly, the 7800X3D is a beast but it runs hot by design. I remember when I first built my rig, I was obsessing over every single degree until I realized my case airflow was actually the main culprit. Swapping the paste definitely helps, though. I have been using Thermal Grizzly Kryonaut 1g for a few builds now and honestly, I have no complaints. It has a high thermal conductivity rating which just works well for these chiplet designs that concentrate heat in such a tiny area. Another solid pick if you can find it on sale is Noctua NT-H2 3.5g, which is super easy to spread and doesnt dry out fast at all. Thing is, dont overthink the application too much. Just a pea-sized dot in the middle is usually plenty. If you are already reseating it, make sure you are cleaning the old gunk off with high-percentage isopropyl alcohol first. Getting that surface spotless makes a bigger difference than the brand of paste itself sometimes. My temps dropped like 5C just by fixing my fan curve and using a better paste, so dont give up yet. Youll get it under control, just keep at it.

TL;DR: Switch to Noctua NT-H2 3.5g for better thermal conductivity and ease of application. Modern chips like yours have high heat density, so you need a paste that handles that pressure well. The Noctua stuff is top tier for the price and won't dry out like the generic factory stuff. Also, make sure your curve optimizer in BIOS is set to a negative offset; it drops temps significantly without losing performance.

Honestly, 90C is pretty normal for those chips, but swapping paste might shave off a few degrees. I usually just grab whatever is reliable and cheap at the shop tbh.