Lagging and freezing despite good config, please help

Hello guys,
I’m doing an interior design project and I’m working towards photorealism and PBR materials, here is the file :

(Link lasts a week, feel free to ask me if dead link)

The thing is, I can barely work, every action causes an horrible lag and I tried a lot of things to remove it.
I’d really like to know the cause of these lags.

I got a Intel i5 3.2Ghz and a RTX 2060 Super. After tests, I can actually rotate objects with 10.000.000 Tris, without too much lag. So it doesn’t look like a “high poly” problem. Regardless, I did some optimization with the decimate modifier but it didn’t help much.

I noticed a very low disk usage when lagging (2Mo/s), and it seems to be related with PBR materials manipulation. But I have no idea what to do to optimize this.

One thing that can help is to turn off auto save in the preferences.