I use a gen 9 IPad with my Lumin U2 Mini and Qobuz and agree that the Lumin app is not really intuitive when you first start using it but you get used to it quickly. Not sure about playlists as I don’t use them- I usually store titles to favorites and go from there.
I believe the Lumin app supports laptop use as well- you can start with the link below. There is also a dedicated forum thread for Lumin at Audiophile Style that gets attention directly from professionals at Lumin.
I would definitely use it a little more before spending more $$ just for a larger screen (unless you need a laptop upgrade anyway).