...
is there a way to render new textures smoothly, without catastrophic FPS drop?
Use "Limit textures size" option.
But it doesn't cure the issue, just makes freezes smaller and IN COST of image quality. The same way I may decrease quality in jpg file, but i need resolutions like 1K*1K
The only solution it seems for me is to display all textures somewhere in front just from scene start. Then it will be no freezes during navigation.