Because I'm not happy with the current browser landscape, I've been working on my own browser, including rendering engine, from scratch, but is isn't ready for use yet.
Most other browsers with a similar feature set to Chrome are based on Chromium (like Chrome itself). If you want lightweight, try a text-mode browser.
It is not lightweight by default, loves to use memory and cpu cores (and now even gpu) when possible. But doesn't use excessive amounts.
I am not a regular user, my Firefox would often have hundreds of tabs open. But performance is not impacted one bit. Background tabs do not take much memory or slow browser down until you get to them.
Of course with any browser try to use fewer extensions