The 16" MBP has a huge battery and should have excellent battery life that's only bested by the more efficient M2 version. You have the storage and memory you need on that, and you can run Logic with all your plugins (the iPad version does not currently support plugins AFAIK).The MacBook pro is great, and i spend most of my time working off of it, Battery life is great, for me its a deal breaker, as we only have 11-12 hours of power a day where i live.
What I am saying is, that Mac can do nearly everything you need, I don't think you need the best iPad Pro just for a few iOS apps. The M1 Air still supports USB-C and USB hubs, though without Thunderbolt support, or the smaller iPad Pro since that has more storage. If your iPhone can handle this, surely a cheaper iPad would suffice... the 8GiB RAM iPads at least today can do everything that the 16GiB models can do. I am sure 16GiB would be more future proof, but 8GiB is a lot for iPadOS even over the next couple years.
I found that iPadOS keeps closing/"refreshing" apps for no good reason on the 8GiB model, and from the reviews/tests I've seen the 16GiB model is no different. Thus I believe iPadOS currently has more optimizations for the <=6GiB models, whereas with 8GiB+ it might not use it too effectively.
It's unfortunate that there is no way to see actual memory usage on iPads because Apple does not allow it. Otherwise it would be simple to check what apps use, standalone or during heavy multitasking and so on, and then base recommendations on that. We currently have no idea if the 16GiB iPad Pro even uses any of the additional RAM right now. Maybe it's being used already, or maybe it won't be used until some new iPadOS version in the future.
(From a performance perspective it seems the memory is completely wasted...)