Speed-up your Mac? Safest and easiest way is to minimize hard disk inputs and outputs by not using apps that use too much I/O.
Simple I/O check in Terminal reveals all the activity:

additionally checking resources usage

shows memory and CPU usage.

As far as Browser goes - Firefox and Chrome each using much more resources than Safari.
On the top of that Chrome is a big snitch reporting your every move to Google - huge privacy leak!There's no place like ~