TestComplete is very resource hungry

Not negating your experience.... something is obviously going wrong.

However, I have a machine that has considerably less RAM... and I'm not having that problem.  We have VM's that we use as our development environments that don't have that issue and they have less resource even than my machine. So, I suspect that he problem is not necessarily SPECIFICALLY with TestComplete but some combination of configuration settings and environment. 

Since you're running on Windows 10, there's a setting that MIGHT help.

Go to Tools -> Options -> Engines -> General.  There is a setting that says "Enable support for testing Windows Store applications".  TestComplete, with that option checked, operates a bit differently against Windows 8 and Windows 10 operating systems.  I've seen major improvements in performance with turning that option off.

Another thing to check is under Tools -> Current Project Properties -> Open Applications -> UI Automation.  There is a check box beside a straight "*" option.  If that's checked, that will slow down object recognition and other performance factors of TestComplete.

Also under Current Project Properties -> Open Applications -> Process Filter, you can instruct TestComplete to only interact and recognize certain system processes.  By default, TestComplete's object browser lists and interacts with EVERYTHING running in the OS.   You can set this to only treat certain applications as Open applications which may improve TC performance as well.

There could be any number of other factors that are causing TestComplete to consume such high amounts of CPU on switching projects or performing tasks.   Again... your experience is not being discounted, but there are quite a number of users here who have been using TC versions for a long time (I've been using it for over 16 years across various versions) and your performance problems have not been our experience.  So... again, means that there's something unique you're dealing with.

There are ways of determining what's going on.  There's a utility that comes installed with TestComplete called "ReportGenerator" which basically does a profiling against applications, including TestComplete, to see what might be going on.  If you utilize ReportGenerate and create a report file, you can send that off to the SmartBear support team and they can evaluate and let you know what might be going on.

Obviously... it's all your choice.  Do what you feel you need to.  But I think you may be jumping the gun a bit "threatening" to drop the tool until the problem has been fully evaluated.