This is my new account and was here since my galaxy s2 and I really looked deeply into the matter.
Improved to an S4 later and tuned the hell out of it. And now having an S7.
The Hardware and the processor improved really much since then, so it's not an hardware issue, it's allways a configuration and software issue, if the phone lags.
I can't understand why people are unhappy with their phones, that aren't "snappy" enought.
It's their fault, because they accept the default settings most of the time and don't care about improving their phone by themself, by optimizing settings, disable useless/unused features and remove all that bloatware and spyware crap.
Also with a good custom rom most of these problems are solved anyway, even by default if the developer did the optimization for you... lazy ass
Maybe start with something like that:
Activate Beast Mode on Galaxy S7
watch?v=nHEm50oRsNs
ps: can't post full links yet with this acc. lol