I also use all mentioned tricks for rendering I normally use very low quality environment and render it in 720 for more than 1 char I also planning on buying 3060 with 6g vram is it good?
There's a 3060TI model with 8G of VRAM, and there's a normal 3060 with 12G. You would be much better off with the 12G version as VRAM is MUCH more important for rendering as when you use the GPU, it runs shader programs which are run directly on the GPU itself and they can only use VRAM effectively so you want as much video RAM as possible.
I don't think there is a 6G 3060. Get the 12G version, I think it may even be cheaper.
All my latest renders you see me post use 500 iterations with denoising (I denoise the last frame and turn quality off). But I have also done 400 iterations and with my 1050TI, I done between 100 and 200 iterations with denoising and that was actually just fine.