You're digitizing analog information.
For that use case your speed and workspace memory resources are über-important.
1. Max out your computer's RAM complement regardless of what computer you get. Take it as a given - for music apps, RAM is the biggest bang for the buck. Anything that will fit into your memory space without needing to buffer to a drive is a big win.
2. A faster processor may make a anywhere from a moderate to major improvement depending on what you're doing. For straight recording you can get away with a slower processor although latencies will be affected. But once you get into plugins or synthesis or modeling you'll need all the horsepower you can get. So if you plan on doing production and mastering, get the faster processor.
Since you can't upgrade the processor (or in some cases the RAM) in an Apple product, you're usually wise to get whatever Apple you buy fully maxed out.
3. SSDs are really nice. Once you get used to them you'll wonder how you ever worked without one. Their cost is high per megabyte, and there are issues with duty cycles and long term reliability compared to traditional hard drives. But they've improved a great deal in the past few years and their cost has come down. Absolute storage size isn't a major concern since you can (as in will) always offload project files to an external drive. Most savvy recording types only use the SSD for the operating system, their music apps, and whatever project they're currently working on. And they're meticulous about backing things up to external storage. I use both an external hard drive and also a free 50Gb account at mega.nz for long term storage. (note: I recommend Mega very highly. Generous free plans. And their paid plans are very reasonable. Only difference between the two is maximum storage size. Disclaimer: I’m just a customer. I have no affiliation with the company.)
4. All computer configuations involve tradeoffs. Never enough money. Never enough resources. So you need to balance wants against available funds and do a little triage.
I’d recommend spending your money on: (a) RAM, (b) CPU speed, and (c) a solid-state drive - in that order.
At least that’s what I’d do based on my own experience with music software and a career in enterprise IT.
Luck!
