Nice review and songs!
A suggestion if you don't have speakers connected to the Focusrite,
so you want to capture with the Focusrite and, at the same time,
hear through the computer speakers.
I have recorded lately in a similar situation. What I do is choosing the
USB card as the Interface in the Parameters tab. Then, in the advanced
tab, I select "Capture only" in the Audio field. No need to define
the input and output device fields as you have already selected the interface
in the other tab.
For the computer speakers to work, I then use "alsa_out" like this:
Setup --> Options tab: Execute script after start up:
alsa_out -dhw:PCH &
Now, jack and ardour will see "alsa out: playback" ports, which are the computer speakers.
For a technical background on this, see:
You mention using solution number 4 but
"this approach will not do any clock drift correction, so as the two devices drift over time, you may get glitches in the audio stream. Nevertheless, it can be an easy if unreliable way to set up JACK so that, for example, it records from a USB microphone and plays back via a builtin audio device".
The solution I described above is the number 1: "If you are using JACK on Linux and want to use additional devices that have ALSA driver support (i.e. most PCI, USB and Bluetooth devices), then this is the best option".
For editing and mixing with the computer speakers, when I don't need the USB card, I prefer to start jack with the interface PCH (the onboard audio card) in "playback only mode" and, of course, disable the "script after startup".
Sure, it is better to connect an amplifier and a pair of speakers to the USB card. In this case, I just start jack the simple way; Interface: hw:USB in Duplex audio mode (again, there is no need for choosing input and output devices separately in the advanced tab)