How do you optimize your archiz scenes for low-moderate hardware?

Okay, so I have an archviz scene in UE4.24 which was made in 3D Max and brought into UE using datasmith. 90% of the materials are made in UE4 using PBR textures, or megascans/substance library.
The walls are separate and everything is static except 2-3 plants.
Skylight is static and has a HDRI image for illumination. Directional light is stationery
I have used 2k textures at max, no more than that. On a few models like some chairs, floor, and ceiling, I have disabled mipmaps but all else have them.
I have like 10 master materials and 82 instanced materials. But I still get texturestreamingpoolsize above budget error. I raise it to 2000 and everything goes back to fine again.
The scene runs at 30+ fps at almost all times inside Editor but when I package it, I get issues on m system. It is not able to load all textures. Some textures look blurry. and also the screen looks like it is refreshing every frame so slow as I can see horizontal lines whenever my player moves.

It seems pretty weird considering that I have created previous projects with ray/corona materials imported from Max and then tweaked a little and those projects turned out fine after packaging.

Check the screenshot for stats on draw calls and triangle count. The shader complexity is also good and the quad overdraw is also less.
What do I need to do to optimize it for better performance as in future I might be doing heavy scenes than this.

My system specs.
Ryzen R7 1700 at 3.0 Ghz
16 GB DDR4 Ram at 3000 MHz
GTX 960 2 GB
250 gigs Crucial MX500 SSD

It has a really high polygon count, close to 2 million, so that’s something you can look at.

The horizontal stuff going on when you’re moving around is frame tearing, it’s what happens when the frames are updating at a different timing than what the monitor is trying to display. You can turn on V-sync to avoid that in which case it forces the game to only sync frames when it can sync with the monitor, but it also has an impact to performance.

Thanks. Enabling V-sync fixed the screen tearing issue.
And any ideas on how much poly count to aim for? Most of these models are from 3dsky and I am not really that great in modeling so I download most of the furniture. Sometimes I use pro-optimizer in 3DS Max to reduce polycount but when it starts creating artifacts in the model I don’t use it on such models

@ darthviper107 : Just checked an old test project of mine and it has 2.6 million polys but it had turned out fine. That project had most materials imported from Max/Vray and some substance materials. No megascans