Back in the olden days we printed 30x40 Iris prints from all kinds of what would be considered marginal files nowadays. They all look fine, a 30x40 print is hanging over my desk ~ it was scanned on an early Kurzweil greyscale only flatbed circa 1990, longest dimension was only 4000 pixels. I have similar large prints from things like first generation Kodak Photo CD and 6mp digital cameras. Heck I did a 14x44' billboard ad using a 2mp small sensor camera in the late 1990s (billboards are lower dpi than you think).
As long as you aren't comparing side by side with the ultimate of ultimate files it won't matter. Especially with atmospheric subject matter like you are showing, that should be very forgiving. If you photographed lawns and wanted to count blades of grass then I could see the requirement but fireworks smoke and such has some margin of error. Think of Gursky, Wall, or Crewdson where they made giant prints and you can read the ingredient label from a tiny box off in the corner of the frame... but even those run out of juice and go to mush at a certain point.
When I'd print for other people it was tonality and focus that were the root cause of 99% of lousy images. Most people don't understand how to set a white and black point and think they prefer mush, even "professionals". Seriously sometimes ad people would embed thumbnails rather than full size images into their projects and yet the thumbnails were not always terrible!
I'd use the camera that gives you the best focus on clouds, smoke, and nebulous subject matter and let the resolution fall where it may. There will always be someone shooting higher resolution that you are, no matter how much technology or money gets spent, because even if you stitch 48 frames together to make a 6tb file there is some nut out there stitching 64 frames to make a 10 tb file.
I haven't printed on the current metal media but again (I'm not that old, sorry to sound like it) the early stuff had a tooth that was more forgiving than the slickest glossiest stuff. If you're spending serious money on these larger prints I'd run tests.