I actually bought a
2015 Phanteks full tower case for this sort of reason, good air flow in early 2021. You can mount a total of 14 fans with it. It's also designed for liquid cooling.
Specs:
L X W X H = 600mm x 250mm x 650mm
Weight: 17.9kg
A LOT of cooling fan mounts.
Back then around 2012, I bought this full tower called
NZXT Switch 810. It has a weight of 20.6 lbs. Boy it was so damn heavy, it feels like a refrigerator. It was hay day back then as well when Phanteks and NZXT were duking it out. It had a lot of swappable drive cages but doesn't have as much fan mounting (only
6 fans in total). If I recall correctly, I think this case doesn't support liquid cooling though, but rather more of a traditional air cooling. It didn't have a bracket for mounting a reservoir for liquid cooling. That was my first taste for a full tower.
I ended up ironically not using it and swapping it for a NZXT H440, which was a lighter midtower. I know it was a waste and naive of me, but I was still relatively fresh to PC building back then in 2012. Much has changed since then. Currently selling my H440 now on the used market and have "outgrown it". That's when I made the jump from the NZXT H440 to the Phanteks full tower case that I have now.
If you want something that's extremely large right now, nothing still pales though in comparison to a Corsair 1000D, that thing is a beast.
L X W X H = 695.96mm x 307.34mm x 693.4mm
Weight: 29.5kg
You can build 2 SYSTEMS in this case.
Just my 2 cents: if you get to a point where you're comfortable already with PC building and maintaining your own PC, you can opt to settle for these large heavy duty cases that have a lot of fan mounts or is ideal for custom loop liquid cooling if you want to and have the budget to spare. Full towers are sort of a dying breed though I feel, I haven't seen NZXT release a full tower lately yet. They also provide you a ton of room for maneuvering and installing components.
I also think that it's natural for beginners to start small first before they take the bigger steps and evolve. Like, I wouldn't advise a newbie to PC building to buy a Corsair 1000D or any full tower for that matter right away and expect him to be able to comfortably build his PC (and you have to deal with that ton of weight). There's a progression associated to it, prior experience makes everything less difficult and is extremely valuable (Example: perhaps you wouldn't mind how heavy is "20.6 lbs" until you actually have the case and feel how heavy it is for yourself as a beginner, and then you decide to fine tune your choice to a lighter but taller full tower which is what you get with experience.). Just my opinion, nothing's set in stone.
I find myself no need to bring my PC to a repair shop (they're much sloppier in handling components than I do) and even installed my CPU heat sink fan backwards.