When making a huge game, what are some VR Optimization techniques?

Here's a breakdown of my game. tons of characters, tons of textures, terrains, grass, cars, traffic system, effects and fire. background(low res) as well as higher resolution interactive characters. Many environments but broken up in small little scenes. . Will use various products with scripting from the Unity Asset store. Some particle effects, some water textures, . Lot of animations for characters.  LIke i said lots of characters maybe even 100 but not all at the same scene at the same time. There's a product in the asset store for weather system and day night cycle. i will use that. there's a product for ppopulation   walking in street lots of people but i believe they are low res.

bookstores, libraries, parks, forests. , shopping malls.

Anyways, it's huge plus have many sounds and sound effects.
What kind of things should i do to optimize the game. Whihc will be played only for myself on a Win 10 machine 32GB RAM  i7, . 

and i'm using DAZ Characters which i will decimate.