Aside from all of the excellent feedback so far on model sizing as a critical feature of efficient modelling, I can offer some advice on V-Ray hardware requirements.
Unless you can afford to spend a huge amount of money on a new Mac you will struggle to use V-Ray effectively. I have an iMac 27 with decent spec but even with fairly simple SU models, lighting and textures, V-Ray was super slow and crashed often.
3.8 GHz Quad-Core Intel Core i5
8 GB 2400 MHz DDR4
Radeon Pro 580 8 GB
Following extensive research and seeking dozens of opinions, I realised that a £5000+ Mac setup might be able to do a decent job but for £2000 I could get a PC to do a great job. Reluctantly (having been a committed Mac user for 15 years) I specified and bought a custom built PC. It has proved a great investment even after a couple of months in terms of render output. Having a reliable and quick interactive rendering option has changed the way I am able to design.
I still use the Mac for everything except modelling and it is great but having a dedicated modelling station is a better setup for me.
One of the best resources I found in gaining an understanding of what makes a good render station is https://www.cgdirector.com/
The balance of cost and performance is not that straightforward and to get the right machine depends on what you want to use it for - static rendering, animation, film editing, 3D modelling etc.
My setup suits my needs on a budget and took compromise to get the right balance of cost and performance. The basic specs are in my profile if you’re interested.