Large scenes in Verge3d?

Sorry for the stupid question, but how do you implement a dynamic or even interractive background huge enough to take up the whole scene, especially with multiple animations playing simultaneously, without lag or slow load times – imagine the following as a blender 3d creation, with traffic flowing sometimes at consistent or erratic speeds:

Examples:

If I just rendered one huge image for the background scene, including the physical platforms the game stage takes place on, wouldn’t the texture become very grainy and blur when zoomed in?

If I put in both game platforms and background scenes made out of vertices, the lag/slow loading times would be immense

Any suggestions for me to render huge, dynamic (background) scenes like the above with multiple animations playing simultaneously with as minimal lagging or slow loading times as possible?

Such as tricking Verge3d into reducing vertices (in real time) without affecting visual quality of objects or by taking a huge as possible image of the entire Blender scene as stage background that is still sharp and clean when zoomed in while allowing dynamic animation to play