Do I need to run the CP4 balanced, or would unbalanced be fine?

Unbalanced is fine

Is firewire that much better than USB?

For many years the difference was about the number of audio channels. It used to be if you wanted to have scores of audio channels, FW was far superior. It simply had the bandwidth to handle it. The old mLAN system supported 100 audio channels in a network via FW. But for what you are describing there will be no advantage to go with FW. As short a time ago as five years USB systems had limited audio channels. Stereo, dual stereo, six channel systems were about it... But now 16, 32 and even more audio channels are available via USB.

Is the software just a matter of preference and aesthetics?

A lot of it is comfort zone, but the audio driver, and how the software manipulates the data can make a huge difference in your results.

I would be just fine with a bundled interface/software. I like the layout of the Cubase vs. Abelton. I've been told to use Logic Pro X for the Mac. After using Cakewalk all these years I'm sure anything will be an upgrade.

You can hear what I'm talking about by taking a .Wav file that you know... Drag that file into the DAWs you are considering - play it back... No special plugins, just playback the file.

You'll hear what I'm talking about. If you have a competent music store in your area this comparison should not be difficult to pull off. You'll see why many folks hear the difference and use Cubase. Plus your Cubase Project can be run on either a Mac or PC if ever you need to take it some where for Mastering, etc.

Let your own ears be the judge. In reality one is not easier or more intuitive to use...in my opinion that's urban legend. At one point in my career I had to use all of them... Cubase/Nuendo, Logic, Cakewalk/Sonar, Digital Performer... They are all professional software, and mature programs. They each have a learning curve, and once you learn it they're all equally easy. So people who direct you in that way might also recommend a tricycle because a two wheel bicycle has a steeper learning curve. Well congratulations, that is true, but it's a poor reason to stick with the tricycle. 🙂 if you get my meaning.

I just don't believe that much in recommending something just because it's "easy" - every thing is easy once you know it (like riding a bicycle, the learning curve is quickly forgotten (as long as you didn't break any bones in the process).

Please re-read my message. I never mentioned anything about what is "easy", just what suggestions for an interface/software to run on my iMac in my scenario. I don't want "easy", just what would be a good solution with all the choices available. For example, I am really leaning toward the Yamaha A06, but are there other interfaces that might work better for me. Reviews favor one over the other for different reasons. I'm just looking for those who have a set-up similar to mine that can offer their suggestion.

Please re-read my post, I'm saying when you ask for a recommendation about software DAWs you will typically receive lots of replies about how easy or intuitive people find this software or that software - they even do that about computer types. I know what you asked - and you did not say anything about easy, (I did), I still recommend you make the decision not based on "preference and aesthetics" but on how well the sound quality is reproduced. Not, repeat, not based on anything but sound quality.