I posted that I display prints in a gallery up to 17 x 22 taken with a 22.4 MP camera (5D Mark III). So why would the difference between 26 and 30 MP be a dealbreaker, let alone for a novice? The fact is that you won't notice it at all. To display on the web, you will end up throwing out 3/4 of that detail.a drop from 30 to 26MP is far from a deal breaker
The Mark IV isn't what I would call "old". It's been out a few years, but it's still the newest in the 5D series, and it's better than anything I have used in the dozen years I have been doing digital. In fact, it's better than anything I have used in the half century I since I first picked up an SLR. (that will change when I get mine later this week.) It's on sale now, but it's still $2,000. IMHO, it's nuts for a novice, but hey, it's your money. On the positive side, if you like it, it should last. They are built like tanks, and it will take you a long time to catch up with its capabilities.
Fine art photographers these days are mostly printing on "fine art" papers, which are very high-quality matte papers. Almost everything I have on exhibit is on a baryta paper, which is a coated paper that preserves detail better than fine-art papers. The gallery where I exhibit has several photographers, and I think only one displays at greater than 17 x 22. All but one of mine there are smaller than that. None of the photographers with whom I have exhibited use metal, although some occasionally use what is called a metallic paper, which is just a type of coated paper. I do have a couple of metal prints in my house, however. They are great for humid environments.
Re printing being intimidating: yes, it's a bit intimidating at first. But the real difficulty, after you learn how to use the camera, is not printing; it's postprocessing. I've been doing this a long time, and I still have a long list of things I need to learn or to practice more. I can spend hours working on processing a single image, but once it's done, I can get the printer started in minutes.
I think I have nothing more useful to suggest.