I've got a 27 inch iMac, quad core i5 at 3.3GHz, 32GB of RAM, running Sequoia via OpenCore Legacy Patcher. By rights it should have gone in a skip by now. The internal Fusion Drive is so slow it's basically a shelf for things I never open. So I plugged in a 2TB Extreme Pro and made it the boot drive. Over a year later it's still my daily machine. It boots off USB perfectly. No fuss, no hangs, no weird permission problems, and the difference in feel is night and day. The Fusion Drive is now just dumb storage. Everything that matters lives on the SanDisk and the whole machine behaves like a much newer computer. Worth being clear about what it can and can't fix. The Mac still has limits that no drive solves. Some newer apps have started falling over, the Claude desktop app being one. That's the CPU and the unsupported OS, not this. But for everything else it's given a beautiful screen and a decent machine several more years of proper working life. I hammer it. Big files, constant read and write, running as the system disk which is about as hard as you can push an external drive. It hasn't skipped once. Five stars. Cheaper than a new computer and it did more than a new computer would have. If you've got an old Mac with a tired internal drive, this is the fix.
