256GB is the perfect SSD size. When you will taste SSD you will not want to go back to HDD. You can perfectly record on your SSD. The only thing you need to have in mind is you have only 256GB. When you start to get 200GB in used it's really time to move things/clean things. (that's the lazy way but it's ok)
The better is to buy a HDD in USB3 working nearly as fine as thunderbolt, but if you have money go. Rugged Lacie is cool but my configuration is not like you. But the Road you still going to take should suit yourself better.
Mine is that. 256GB for my Operating System. Every VST User folder is symlink on a Audio HDD (2 TO USB 3) and my studio libraries (from VST) are installed on this HDD. Sample too, collection and my personal Sample collection folder.
Then I have a Data HDD usb3 (3 TO) Where is stored Data unlinked to Music. Like Software setup, my documents, Backup (which is stored also on Audio HD)
I Record audio on my SSD system. But i never let something on my SSD drive, i always move things to Data HD or Audio HD. My desktop is usually empty (when it's not it's temporary) same for Music, Movies, Download, Documents etc... Why is that ? Because when i want to restore my backup i don't want to think if i will loose something in the process. As i modified my way to working on a computer i never loose something now.
Edit : You can buy a small External SSD for record audio if you want, you setit up as your work hd in your software where it's temp, rec audio etc... if you want.
I also make backup for Audio HD >> Audio Clone HD (never in used only here in drama case)
I also make backup for Data HD >> Data Clone HD (never in used only here in drama case)
Now you can say wow you're psycopath