Well in terms of protecting data and speeds I would say get to different SSDS. One for OS and one for Data. This is standard for many reasons but the two biggest are that, you can write and read from both drives without effecting speeds. Such as OS reading data and a video game or video on the storage disk reading/writing data without slowing performance. Another reason to have two drives is incase the OS drive dies. You'd be able to pull out the storage drive and still retain all your data.
I would recommend getting a smaller drive like a 250gb or 500gb for your OS and only install OS on it. Then put your other SSD (1TB or 2TB) in as a secondary drive for data, games, video etc...
Or if you really want just the extra space and don't...