The best free cleaner is no cleaner at all. I know I'm imposing a bit when I say that, but cleaner programs like CCleaner, Bleachbit and more tend to do more harm than good. Usually, your OS will know how to keep itself maintained properly. Sure, there's the registry, which is a mess and should clean itself, but that's something Microsoft should have as a function. A 3rd party cleaner program will not do it very effectively, and may even do more harm to your computer than good.
I've gone through a couple of installs of Windows over the course of my computer's life. For the first year, I've had things like CCleaner and AV programs to help protect my computer. I thought I was helping it go faster. Then I went through an install with none of that crap on, and noticed less resource usage, less problems, and a much faster computer.
My sister just got a new W10 laptop, which is more high-end than my 3 year old laptop. But my laptop boots faster(we both have HDDs), and boots up programs faster, and isn't any slower than hers when it runs programs. Well, her laptop came with a ton of bloatware that I've removed from mine or used a clean install, and it came with BitDefender which I don't have, and some others. I generally don't use programs that will fiddle around with the OS, and I tend to have far less problems.