The best Apple laptop for music production?

[fmr]

And when the decision is between power and portability, always choose power. (Which also calculates into its technological life span.)

... and be prepared to toast your desk (or your knees... or your laptop).

[Tj Shredder]

The newest models you can't upgrade, but buy just into what you need now and for the next year. If your need is not top of the line consider a used older model over the same specs of a new model. Easier to sell later if you need more power in one year. Do not buy older than three years, the price/performance ratio is good between 1-3 year old Macs, the older ones are usually more expensive for their expected life span... (older models do not force you to the latest MacOS...)
The bigger internal drives are over priced always, an external thunderbolt 3 PCIe drive would be fast enough (almost as fast) and could be cheaper with housing than the bigger internal drive...