"Thanks for the detailed reply and link to the review. The Maggie Cameron video sounded good. Do you have any video that includes vocals?"
Thanks for the comments. I did that video to demonstrate what a $50 set of "Matched Behringer SDCs" were capable of.
There are other videos on my Youtube channel that have vocals included. Most everything on there right now was done as either overdubbed multi-track or live multi-track recording using the Zoom R24, although the L8 sounds pretty identical with a bit cleaner preamps when using higher levels of input gain. Here's a live recording done with the R24, track editing and combining with video in Reaper:
"I'm not convinced of that. As long as the interface unit isn't too large. I'm a retired software developer so am used to using computer and do a bit of video editing using final cut, I guess having more control is what I'm after."
YMMV on computer use. I find all of the little steps you need to look after when using a separate audio interface, computer, and DAW interfere with the creative process. When recording I personally like a dedicated recorder that lets me spend my energy on simply laying down good tracks and not spending time on input gain balancing between interface and DAW, file management, handling multiple takes, yada, yada. As long as you're comfortable devoting time to what it takes to using the computer I'd say do it.
As far as having more control, I love having "control" and find it's great to do that... post performance. That's what DAW editing is all about. All I really want to have control over when capturing audio is input gain. Concentrating my energy on performance is something I need to do if I want anything good to go down on tracks. (YMMV, of course.)
"I've also looked at devices like the Scarlett 2i2 and Presonus Audiobox, am concerned they have 2 few input channels."
If you want more than a simple two input interface it adds a fair amount to the cost and setting up the inputs to the DAW adds time and increases the chance of making simple mistakes that can effect capturing an otherwise good performance. Those are choices that only you can make.
"Perhaps I need to better understand the multi track recording process. If there are good resources / tutorials to suggest I'd appreciate it."
There re oodles of Youtube videos. The basics of tracking are pretty easy to find information on. There are several older forum posts right here on AGF answering basic questions about microphone selection, positioning, gain structure, dealing with the acoustics of WHERE you record ( a BIG influence on the quality of your recordings) and quite a few topics dealing with the process of capturing good audio while recording audio and how to combine them to make good Youtube videos.