Now I'm using my old laptop for graphics work. For more heavy intensive 3d work I prepare 1 years my savings money around $5000 and want to make a PC in this price area with latest i9 13900k and RTX 4080 but I'm confused with ram selection. I don't want to cost-cutting in majore part of the pc that's why I'm confused to select ram in between 64gb and 128gb. Maybe I'm pick 6000MHZ stick of ram. Is 128 Gb ram help me everytime using blender normal to heavy work? Or should I consider 64 Gb? In internet I found many of the tech guy recommend 64 instead of 128gb, But other recommend 128gb as well. Now I'm confused to spend more money on 64gb more ram. Is 128 Gb will good or worst idea for me?
No, RAM will not make rendering faster. Amount of memory will not improve speed of the rendering, only make it possible to render large scenes. 128GB is needed only if you render extremely large scenes or very high resolutions and RAM will only be used by CPU rendering. If you render with GPU, you want to fit the whole scene into GPU memory to enjoy all the advantages of GPU rendering. Even when working you will most likely not experience any improvement in performance if you have 128GB of RAM since what you see in the viewport will be limited by GPU. It will make various ways of processing large amounts of data possible though. If you need massive simulations, and large amount of detail in your scenes like plants, grass, hair, particles and so on, RAM will be needed for you to be able to work with that amount of data. RAM is usually not about speed but about what amount of data it is possible to work with.
If you need to ask, chances are, you really do not need that much RAM yet. I would advise going with the smaller option since 64 GB will really be enough for mostly anything and it is always possible to upgrade if you ever need to. Unless of course you have a good reason you need that much RAM.