MBP mid 2010 upgrade for logic pro x

Hi every one.

I have been struggling with my MBP mid 2010 ( 2.4 Ghz i5 8GB Ram) and logic pro x for a while, to the point that I haven't recorded for a while.

I am having a pop up windows telling me that I dont have enough what so either while not having that many tracks. Usually about 10. but mainly lots of lagging while recoding instruments, which makes the experience almost impossible. I know my system is quite old. Only usb2 and firewire, which both are quite slow compare to today specs.

Also One need to know that I do video editing on premiere pro, but use an external drive for storing the files. It works just about.

I was looking into upgrading the hd for ssd and maybe swap the optical drive with my hd of 1T (a hybrid ST1000LM014-1EJ164), or adding a second ssd? and taking advantage of the bus speed which i don't think I can achieve with the usb2 or firewire. Tell me if I am wrong!

Here my questions.

What is the best setup. System on ssd and data on the hybrid? or System on the hybrid and data on ssd? or should I benefit from 2 ssd. I had in mind 2 Crucial MX500 500G which are reasonably priced.

Where do I put my plugins? on system or data. I use mainly BFD2 (which has a 250Gb of recorded sound/sample), and native instrument Guitar Rig 5.

Many thanks