How big of a speed difference will be noticed with a 100-200 MHz overclock?
It's impossible to tell, the effect of overclocking varies depending on the specific software and hardware. 

However it likely won't make any notable difference if you're only getting 7fps in a game. Overclocking is highly unlikely to make an unplayable game improved to the point where the game becomes playable, except in very rare circumstances such as with games that have a speed budget to decide whether to frame skip and your phone is just barely below the budget which causes it to consistently frame skips and the extra processing power manages to push it to be consistently below the budget.


  some argue that raising clock speed alone doesn't really guarantee better performance, since microarchitecture and bus speeds are what determines ultimate performance.


Performance is a complex thing, but one thing for sure is that CPU is rarely the bottleneck in many applications. Booting, for example, is IO bound, the bottleneck of booting is how fast it can marshal data from the persistent storage to RAM. 

In short, you'll have to try it yourself.