slow running A1278

The "A1278" designation covers a wide range of models & years from 2009 to 2012. What is the exact model? You can get this information by clicking the Apple menu and selecting "About This Mac".

Also, what is the exact make & model of the SSD and memory?

How did you set up your new SSD?

FYI, it is best to only make one change at a time so that you can confirm the modification works properly. Introducing multiple changes at once greatly complicates troubleshooting.

To help us get a better idea of the system run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper. This may provide some useful clues for us as well.

Hello jagdish200,

With your device running slow despite hardware changes we recommend isolating any software issues: If your Mac runs slowly - Apple Support

Select the macOS version most relevant to you in the top left corner. Should the behavior persist you may be experiencing a hardware issue. Please review details about vintage products here: Obtaining service for your Apple product after an expired warranty - Apple Support

Take care.