Originally Posted by theesotericone

I forgot to tell you that wiping cache clears all the optimizations. It used to do that in the background but in 5.1 Google had the bright idea to do it before boot. Luckily in 7.1 they've gone back to letting it do it in the background.

So if your low on space that is probably a big part of the lag your getting. Flash memory likes to have about 25% free space or more to run at optimum efficiency. So if you've got 32GB of space you want to try and keep about 8GB free. The lower that free space to total space percentage goes the worse performance you'll see when apps try and access data on the chip.

The second thing you'll be looking for is the RAM usage. Android does a really good job of allocating RAM so that's usually not the issue. Sometimes though people put a "battery saver" or task killer app on there device. Those apps are complete and total crap and end up taking up more RAM than they free.