Recommended machine/parts for deving on a PC for low demanding games in Unity?

I have a 7 years old machine. It's decent to run the Unity Editor.
However, once I buy a new PC, I want to know what is important for the Unity Editor to run as smooth as possible.
I am using VS 2017 community with Unity Free.

What I mean is things like compilation times and general responsiveness.
For instance, I might edit a script in VS, then I go back to the Unity Editor and look for a different file in the asset browser. Then, after clicking it, there is a few seconds delay before it responds.
What are these delays?
Is this just page flipping from my SSD to memory? Is it the HDD?
I think it's not the HDD because when my HDD wakes up I can hear it.

So what is it? Is it CPU related? Processing.... something?

A big annoynace in working with Unity and other game engines is slow downs and crashes.
It's extremely annoying to have to press play or pause and have to wait a long time for no apparent reason.

So how do I lower those times/delays and if possible Editor crashes?

Notice I don't care for a machine that can run the latest 3D graphics, I am mostly doing low requirement games, but even then the editor might be slow to develop the game with.

Maybe those delays cannot be fixed for unknown reason?

 

Yes. My own experience with the delays you're listing was that they went down massively with my latest upgrade which was a new processor (Ryzen 5 1600X), new motherboard (GA-AX370-GAMING), and new memory (DDR4-2666). My previous hardware (Phenom II X4 965, DDR3-1333) was about the same age as the computer you're currently on.

Basically the delays are the editor compiling scripts behind the scenes and compiling is very heavily CPU-based.

 

I upgraded my very old computer to a slightly old computer.
In a test I did... where I have a script in C# and then I add something like "public int someParm = 1;", it takes about 6 to 10 seconds to process.
The steps to do this experiment are like this:
1) Open the script in Visual Studio
2) add the parameter line to the script.
3) save.
4) Switch to Unity with a component that have this script(this is when the CPU is starting to work and I count the time).
5) Wait till it appears or the CPU gets normal again on task manager.

Notice the CPU wouldn't start working if Unity is not in focus. So I think that's a good hint the CPU is working on that.

So currently with an i7 3770 CPU and 16 GB of RAM(not sure which speed) I get about 6 to 10 seconds just to add or erase such a public int.

It does seem to use a single core though?