No problem.
A GPU is good for rendering, yes, but not for rendering something as detailed as this when your GPU is weak. In games, you generally don’t want anything to have a high polygon count (above ~50k or something) because it’ll bog down the graphics card’s ability to render that item–this is why they do retopology on sculpted items; furthermore, a graphics card renders stuff in an engine differently because everything is loaded into memory and calculation for lighting and the like is pre-compiled, all unlike Blender (you can see on loading screens of games that they do this). For Blender, as I understand, this stuff is in the raw and everything is done at time of rendering. The advantage here is that you can take any complicated object and render it out successfully while mimicking real-world physics for lighting, fog, cloth, etc.
Now, I must ask, what is “archiwz”? If you’re working with VR, there is no difference. I see no reason why you must have an EGPU in general, but if you intend to get a power-house-of-a-card, then the consensus seems to be that it helps. Also, make sure you have a “thunderbolt port” if you ever decide to get it for your computer. As for memory, if you intend to make high-poly models and high-resolution stuff, you’ll probably want to have as much memory as you can get (8gb) because you already have a lot of RAM and you don’t want to be running out of one when the other has plenty of space. There is another thing… you should read this and look at the charts at what difference GPU can make vs CPU.
Then decide for yourself.