This is super important, so good for bringing it up!
I never tested the speed of opening, but I routinely use 4096px and my scenes open fairly quickly. I am tempted to believe the slow-down would be rather due to swapping between GPU VRAM and System RAM. 11GB of 2080ti is still not a lot, because 3dsMax doesn't use any compression at all, so single bigger scene can eat up to 10GB in textures alone and that is just viewport in Max alone, Photoshop, Web Browser, Image viewers,etc. will eat VRAM at same time.
(But now I am gonna test this up)
When you run out of VRAM (you can check this on Windows 10 with task manager, there is GPU tab, from latest update you can even assign different GPU to different task/software), the performance completely tanks as well, if you had 200 FPS for example, you'll get right down to <5 FPS...
I've been on Quadro RTX5000 with 16GB Vram for over a year now for this reason alone. And I am upgrading all PCs to GeForce 3090 with 24GB to make life even easier (though GPU rendering & Unreal 4-5 will be nice bonus).
I have other "trick" people might not know with Corona, CoronaBitmap doesn't use TextureSize like Max Bitmap, but the procedurals! I was baffled why my CoronaBitmap materials look blurry in viewport and Ondra explained it's due to this.
This is reason why I advised people all year to buy 350 Euro 1080ti from used-market, and not brand-new 2070-80 with pathetic 8GB. 3dsMax doesn't care about the speed of your GPU much (in fact it runs fantastically on integrated Intel GPU lol), but VRAM is everything.
And the solution would be so easy for Autodesk... Unreal uses lossy compression for example that saves 75perc. of VRAM, such massive compression introduces artifacts on even spaces (like pure white/grey texture), but who cares in viewport?
I pondered lately if it's not possible to super-impose such compression from nVidia settings override.
In meantime, with Unreal 5 we're gonna get real-time mipmapping and unlimited texture size&amount : /. 3dsMax, on other hand, can be perfectly killed with single 20k texture shown 1:1.
(Would be nice to get that in Corona too, Corona too can be killed fairly easily with shit-ton of 8K textures, and no one uses tiled-exrs).