your question seems to be similar to Why does Chrome has so many processes running, when I have just opened the application?
Multiple chrome.exe processes in Task Manager
the TLDR version of those 2 post are...
Each Chrome Tab opens a fixed number of processes that are equal to the number of extensions.
so if 1 tab is open and you have 4 active extensions then you will have 4 Chrome Processes in your Windows Task Manager.
2 tabs will result in double that number; 8 processes listed in your Windows Task Manager.
So keeping a Tab in your background actually is using up resources.
To access your chrome Task Manager, click on the dots at the very end of your address bar; on the right hand side;
Select More Tools and then Task Manager. That should show you what which Extension or Tab is taking up the most resources.
Hope this helps.