It's good that you've brought up the very key point about this right at the beginning. Unless you're using the absolute cut throat bare minimum of RAM there's no reason why you'd need to worry about this. Android purists and iOS fanboys have gone out of their way to say that AOSP (they include MIUI) are horrible at RAM management and that's just not really the simple case. Android devices are coming with more and more RAM and that's just because they do much more than Apple devices especially in the background. Vanilla android also has to add on all those Google trackers that run in the background of android devices so really you do need at least 3GB of RAM these days. This is why as Apple takes more and more MIUI features into their new versions of iOS that system that used to be so great at managing RAM is glitching and crashing and constantly getting bug reports affecting a large portion of their community.|
Luckily either RAM is really cheap to get or we're just at a RAM marketing era of smartphone selling but all our modern phones have so much RAM to spare. MIUI doesn't really guzzle all that much RAM and especially with MIUI 10 optimizations the management of it has gotten much better. I'm typically rocking 4 of my 6GB of RAM and even in the heaviest cases when I've gotten lazy and left four or five apps open I'll still just be down to my last 2.8GB or slighty more than 3GB used.