I've recently been looking into this as well since I can't get together w/ my friends / band to jam. the other guitar player and I were talking about sharing multi track recordings from our jam sessions and doing edits BEFORE the lock down and I figured maybe we could work on a few songs via recordings and send them back and forth over the next few months.
Anyway, I also got a focusrite interface and tried the free version of Protools they provide. I already had Guitar Rig installed (which I rarely used) but couldn't figure out how to make the plugin work with Protools. After spending a considerable amount of time trying to get it to work I figured out that plug ins are disabled on the free version so you have to buy the full version. Pro Tools is pretty expensive so I bailed on that. But my friend had been using a free DAW called Tracktion 7 for months and doing all our recording edits with that, so he suggested I use the same tool to make collaboration easy and to avoid any issues compatibility issues. So I installed Tracktion 7 set up my interface and scanned for my plugins and it found Guitar Rig no problem.
But then I found that going straight into the interface with the guitar and counting on the Guitar Rig plug in to provide good amp sounds didn't really work. There was too much lag! It was impossible to play along with the pre-recorded track. I don't have a high end PC but i'm guessing even a high end computer is going to produce too much lag taking your guitar signal from your interface, sending it to the DAW, processing it through the plug in and back to your interface. So to get around this, I hit the live monitoring button on the Scarlet and yeah that works. You can play live to the recording but your hearing your clean / dry guitar signal as you play. Then after the recording, you can add your plug in effects. It works but far from ideal - especially if your part is supposed to have gain.
Next I set up my amp and pedal board and put my SM58 (really the same as SM57) in front of the amp. I plugged the mic cable into my interface and recorded with live monitoring. There was of course NO lag with live monitoring and I could hear live what the guitar actually would sound like on the recording. The results were WAY better than I was getting from Guitar Rig plug in! Of course you can still use that plug in to change the sound of your amp, or effects, or cab after the fact if you want. (I recorded at low volume but a good OD pedal with low gain can give you some pretty good natural amp sounds still. although I'm considering putting my amp in the basement and cranking it for a future recording.)
So I'm also recommending the SM57 as recommended above.
Lastly - regarding Guitar Rig and DAWs. Definitely try to find out if whatever guitar amp plugin you buy will work with your DAW. I liked the free Tracktion DAW but the companies newest product is called Waveform. They have a free version of that as well and I think they are trying to move toward this version and away from the older Tracktion 7. Waveform is 64bit vs 32 bit I think??? The interface seems mostly similar with some minor upgrades and cosmetic changes but I think most of it is the guts of the system. Regardless Waveform seemed to work a little bit better on my PC so I moved to that one. But what I found is Guitar Rig will not work in the new Waveform DAW. Guitar Rig is older and will only work on the 32bit DAW. I considered buying another amp modeler and I still may for some post recording edits, but I decided to stick with the mic for recording.
