Apparently the situation with Windows Defender is better, but not the best. I can suppose why it may get out of control, there are two main reasons: it is in a permanent conflict with another anti-malware program or it continuously checks the state of one or more too active background processes. Sorry I cannot say anything about Malwarebytes because I don't use it; you may try to stop its service and see whether it helps. Otherwise, need to do some more tests. You should try to remove some background programs (secondary drivers, start-up components) and check which one is in conflict with Windows Defender. To do this, you may use msconfig or CCleaner (Tools, Startup, disable here all Windows startup components and all non-Windows services), then enable them one-by-one and see the difference.
I also saw a few situations when Windows Defender "goes rogue" after badly issued database update, continuously checking the system and eating CPU resources, but usually the developers are able to understand their mistake in a few hours and fix it in the next update.
About Chrome: you also need to make some tests to understand the root of the problem. First, clear all browser data for all time. There is a chance that cleanup may help. If not, Chrome built-in Task manager (Shift+Esc) may give you some insight. Then go to Extensions and disable either the suspect or all of them, restart Chrome and check the memory. If you see the effect, enable extensions similarly one-by-one. If even without any extension Chrome consumes too much memory, I can suggest to reinstall it completely, deleting all data and user profile at uninstallation. Don't forget to make a backup of your bookmarks, exporting them to *.html file. After removing all traces of Chrome in the system, install it anew, import the bookmarks from html file and slowly add the extensions.
