How do you power it all? Directly from your iPhone/iPad or carry a USB battery?
I’m asking because something I adore about the OP-1 field is that it’s battery-powered and it lasts sooooo very long. Perfect for train rides and the like in a package very similar to carrying a Nintendo Switch or a Steam Deck. Then again I use the OP-1 as a toy 
Consider that I always carry my laptop with me when I’m around because, working in the IT industry, I will need it 100% of the times, so I usually plug the midi controller to my laptop and use it with Ableton, this is my main use of a portable midi controller.
That said yes, the Launchkey mini can be powered by the iPhone 15, wouldn’t know for lightning iPhones with a dongle, but I power mine just with the cable; I’ve purchased a usb-c to “printer” cable and plug it into the iPhone port right away… there’s a catch though: the iPhone doesn’t have a jack input, so you need a dongle to split it into jack and usb (they’re quite cheap and small), I’ve tried using the airpods but the latency is way too high. On the other hand, I’ve used the op-1 field as a bluetooth midi controller on the iPhone and have been impressed by the latency or better, the lack of it… so I was also considering one of those tiny bluetooth mini keyboards, didn’t get one though because well… I can use the op-1 field for that 
Ah, since we’re at it, I ask you the same thing I asked to another commenter: what are your headphones of choice? I have some bulky Audio Technica and I wanted something more portable.
I use a pair of Sony MDR-EX650AP earphones and I absolutely love them. My first pair lasted me 8 years and when they finally gave up I spent a stupid amount of time researching alternatives and ended up buying the exact same model again. I’m not an audiophile though!
I bought the Sennheiser IE4 a few years back, they’re in ear with a few different tips, and are basic but very good / flat sound quality. There are more expensive options but these i’ve been happy with. The Apple ones are fine and have the microphone but I’ve done vocoder things using the Field’s built in mic which sounds a lot better, when using the earphones to disable the built in speaker and hear what I’m doing. Like this quick vocoder test:
EDIT: Oh and since people are talking about USB-C power, that’s one of my favourite things about the Field. It can power the Arturia Microfreak (which I’m probably selling, too much gear!) and it can power the Micromonsta2 (never selling that!) and it can also power and communicate midi over USB with the Squard Pyramid sequencer. It’s super handy. Have on occasion with a lightning cable digitally recorded from my iPhone into OP-1 Field also.
Honestly as soon as I heard you have push 3, my thoughts are sell op.
Yeah, on the other hand the push 3 is not portable at all, unless by portable you mean that you can move the thing around in your house
In terms of headphones, i’ve been blown away at how reasonably priced, sturdy and affordable this set has been. Amazon.com