''You can set the optical SSD to be your boot volume''
'''There are many reasons that a machine "slows" down.''' Depending upon what you're doing it could be a network issue, a swap/free space issue, a fragmented HD issue, a failing HD issue or an issue I've not even mentioned ''(like an anti-virus. or malware using up resources in the background).''
Graphic intense applications require a lot of resources and it's best not to over tax the machine when using them. ''Many former Windows users don't realize that clicking the red dot does not quit all applications (only those with single windows like Disk Utility, Calculator, System Preferences) will quit when the red button is clicked.''
Activity Monitor can tell you which application(s) are using resources.
'''Adding/changing an SSD is not a surefire way to increase computer speed.'''
There is [https://www.ifixit.com/Answers/View/10622/Which+internal+hard+drive+do+I+need|an alternative].
''If this answer is acceptable '''please remember to return and mark it accepted'''.''