Mozilla is beginning to make a series of changes to Firefox that'll make certain aspects of the browser operate a lot more like Chrome. The changes are broadly designed to make Firefox more secure and stable, but they also have the downside of making it less customizable and potentially more of a resource hog.
https://www.theverge.com/2015/8/21/9186809/firefox-becoming-more-like-chrome-extension-changes
If I wanted firefox to look and act more like chrome, I guess I would install chrome (and that for me isn't going to happen). I just can't see their reasoning in making browsers unrecognisable from chrome, what's the point of becoming clones, might as well give up.
As far as resources goes, firefox is already a bit of a resource hog.
Try Pale Moon, I'm very pleased with this very robust and very highly configurable browser with literally the best of support.
Pale Moon is absolutely the ONLY browser on the market with all of the following: Bookmark management, Download management, Password managing, Form managing, Spell checking, Search Engine Toolbar, Per-Site Security Configuration, Privacy Mode, Auto-Updater, Tabbed browsing, Pop-up blocking, Incremental Search, Ad-filtering, Page zooming, Full text search of history, Content Model Dialogues that with all of this also passes all 3 Acid Scores (The Acid tests are online test suites to determine aspects of standards compliance, to expose web page rendering flaws, and to rate the performance of browsers. Upon each test's release, they are designed so that no existing browser can pass without further development. In order for a browser to pass any Acid test, the latest public release of the browser (not an alpha, beta, release candidate, or other version under development or testing procedures) must meet the requirements).
No other browser can claim ALL of the above, which is why I personally rank it far and above #1.