The latest driver is installed.
I found out how to switch it back to DirectX, also disabled all mods and re-enabled some of them.
Everything seems to be sorted now...

No FPS drop in inventory, it doesn`t even budge with an open inventory

Thanks for the assistance

I tried taking screenshots full screen, but something weird happens and it takes a screenshot of the main menu.

I've disabled some of the mods, I noticed the "simulation" mods had an affect on FPS with an open inventory, but there's still a drop in FPS to a lesser degree.

I had a crash not to long ...

These are the 2 that I could find

I took screenshots with gpu timing enabled, didn`t see an option to show enabled mods so I took another in the mods menu.

Noticed some of the values do go up whenever the inventory is open

Recently started experiencing drops in FPS in-game.

Whenever I open my inventory, the FPS drops to Around 14FPS depending on what is happening in the background.
After closing the inventory the FPS counter quickly and gradually returns to 60FPS.
During all this the UPS stays at 60UPS

GPU usage ...