Re: On using external hard drives for recording.
The main thing is to reduce wear as much as possible on your laptop drive by sending the really big writes and erases somewhere else(the external). The biggest thing to put on the external, is just the project files, that all of the individual recorded tracks record to.
The laptop will still be using its drive for the operating system, and for RAM overflow(the writes to and from these two things are the main reason why the additional writes for a recording project put too much stress on the drive - it can only do so much at one time. Make it do more and it will get hot. When hard drives get hot, often, and stay hot for extended periods of time, that is when they will fail. This is all that recording audio projects to a system drive does, all the time.), and shit like that, but whatever you can send somewhere else is good. This mainly just means the project audio files.
I would probably keep the DAW installed on the laptop. Really, in the case of that, i don't think it matters a whole pile, either way. Especially if you are using Reaper, which is designed to run off a flash drive if you want to. You could put it in the laptop, or on the external and probably not see any performance problems(unless the external drive or the laptop USB is 1.0 or a buggy implementation/chipset). I just like to have my program files all in one basic place(in this case, on the laptop) sort of as a habit.