As ss44 says, there is nothing nasty going on amongst the processes.
One or two of them could be happily stopped without affecting things badly, but the saving on memory usage would be minimal.
As you had the slow/sluggish problems prior to the avg-to-avast switch, Avast is not the problem so my comments above are nonsense...
Your concern about being short of space, your wish not to lose more space and your comment about getting "virtual memory running low" rings a bell with me.
When Windows runs out of available RAM as may happen if you have one or two ram-heavy applications running, it may turn to the paging file and use that as a sort of substitute RAM
Paging file = scratch disc =virtual memory .., an area on your hard drive drive set aside for this purpose
If your hard drive is full or getting full there may not be sufficient free space available on the drive to act as paging file...so the system struggles and waits for RAM to be freed up from another source.
I am sure that I read sometime in the long distant past that Windows cannot handle this sort of situation very well if you have less than 10% of your disc space free.
Is your drive very full ?
Can you go My Computer.....right click on the C drive and then click on properties. You will see a wee pie-chart showing free space and used space......can you let us know what these figures are ?