As windows allocates memory for processes?

how it interacts with RAM and the user for interaction to all of this via WinAPI

In this context - in any way.

All programs work with virtual memory - the other is not.
And already the OS itself decides how to interact with the real data store, be it a plank of RAM, or paging file. And you can not in any way to influence it.

Task Windows just to completely isolate you from such things as RAM.

I would suggest the book "Windows Internals" by Mark Russinovich. It describes the process of allocating memory and General Memory Manager.

It is also worth to see how this makes the processor. For example here is a description

Read the help for functions VirtuallAllocEx, VirtualLock and around

As far as I can tell, windows has developed an extremely marasmic situation due to the policy of the campaign according to which they can't divulge the details of the system architecture, it is an open secret, but since all the multitasking OS is more or less similar about the architecture of operating systems are available from competitors, for example there is Russian author Sergei Dunayev, which beautifully illuminates the theme of memory in unicodebig systems here after reading the section devoted to swapping you will not be hard to understand what it means

the paging file size, etc.

because everything is chewed.

Virtual memory is implemented in hardware and software, i.e. without the support of the processor is not enough, so the OS here is not the "trendsetter", but only use the approach proposed by the developers of iron. Of course, the writers of the axes can the same to participate in the design process of iron and often do, we can even assume that the virtual memory has appeared because of the hotelok OS developers. This approach is fundamentally the same that in Windows that in Linux for those Protsiv, as dictated by the specification of the processor, of course different implementations, but they do the same thing.
So I can safely read about it in the literature on how the Linux virtual memory (if you can find), in General, Windows works the same way.
You can also read antalovsky documentation.
But, really, if you are going to develop the kernel, it is sufficient to understand in General terms how it works.

In General, Richter writes well, try to read :-)

Virtual memory is not "interacts with RAM" RAM is an integral part of virtual memory.