The good thing about monitors is that you don't necessarily need to upgrade them together with your PC.
You only need to consider the technology you are going to use in future.
If you buy an AMD graphics card (or a PC with one), you are bound to "normal" or FreeSync gaming monitors.
If you bay an Nvidia graphics card (or a PC with one), you are bound to "normal" or GSync gaming monitors mostly, with a chosen set of "compatible" FreeSync monitors which would work so-so.
Nvidia Graphics cards tend to have considerably more "bang" than AMD cards in gaming, but GSync monitors are quite expensive compared to FreeSync ones (albeit they've got slightly better specs and wider frame sync ranges too).
A Ryzen 5 3600 with a MSI B450 TOMAHAWK motherboard would be a good choice imho.
IMHO any AMD CPU is a bad choice for gaming.
The newest Ryzens might score reasonably in synthetic benchmarks, but they suck balls in real life environments when it comes to gaming still.
Same for single thread performance, which is the most important thing for IL-2 (including CloD and Great Battles).
See e.g.
https://cpu.userbenchmark.com/Compare/Intel-Core-i5-9600K-vs-AMD-Ryzen-5-3600/4031vs4040Intel CPUs are much more tolerant to overclocking too.
My i5-9600K runs primestable on 4.8 GHz (instead of stock 3.7 GHz) without any gongs and tinsel. I've
lowered it to 4.6 GHz only to have some safety margin. No voltage adjusted, no fancy cooling, just raising the multiplier on all cores, period.
The utmost you can usually squeeze out of Ryzen 5 3000 series CPUs is 4.2 GHz (instead of stock 3.6 GHz) but you will need a
massive cooler, raise the voltage and keep your fingers crossed all times. Without such measures, you're stuck at below 4 GHz.
TL;DR: AMD sucks balls for gaming. Don't buy it.
Mike