1. Is my assumption / hope that creating arrangements quickly, then exporting them to Reaper where I will edit them and overdub guitar and vocals, a realistic assumption/hope?
That's what most people do, from past and present experience. The advertising is true. If you know the chords to your song, or are musical enough to enter them on the fly--and it's basic structure--you can get an arrangement in not-too-many minutes.
If you use the part-markers, pushes, rests, shots, and holds (entered right there in the same box you entered your chords) you can get a stylistically accurate groove that isn't painted wall to wall. All that (and more, if you want) right in BIAB. To me, there is very little of a learning curve to do that much.
2. ...Are there any problems with running BIAB from a USB? Freezing? Latency? Anything like that? Will I be sacrificing any features if I go the USB route?
There is an option in the installation to have the program itself sit on your internal HD with the real-tracks, midi, and all that residing on the external HD. That's what I am doing, if that helps.
I'm not incredibly tech savvy, but here's my experience as a newbie with the USB version of BIAB. To generate (or regenerate) the full list of tracks in a "busy" style takes about 20-30 seconds. To re-generate a single track takes about 8-10 seconds. Those would be realtrack-heavy styles. Midi is faster.
I've had BIAB "freeze" and then "unfreeze" a small number of times, but I think that's because my former usage was all midi and I was used to working faster. I've had it "freeze" and fail to "unfreeze" after an extended wait, but rarely--same as other heavy-lifting apps like video production/rendering straight from hard-drive. I've only had it return an error once. It's not yet crashed the computer. Like any work-horse software, just don't push it too fast with multiple commands, and it will behave just fine through USB.
To add: Since I've gotten this version, I'm actually writing the songs in BIAB without foreknowledge of (or the musicality to know) what chord always comes next, or how it will ultimately be structured. So I'm doing more "re-generating" than you might be in your song-writing method.
Last edited by Tangmo; 10/09/18 12:40 AM.