The interface is SATA. I don't know what you mean by "form factor". If you mean the physical size, it appears to be the standard 3.5" drive as show in the teardown: iMac Intel 27" EMC 2309 and 2374 Teardown
We have a chance to guarantee our right to repair electronic
equipment—like smartphones, computers, and even farm equipment. This is a once-in-a-generation
chance to protect local repair jobs—the corner mom-and-pop repair shops that
keep getting squeezed out by manufacturers.
Join the cause and tell your state representative to support Right to Repair. Tell them you believe repair should be fair, affordable, and accessible. Stand up for your right to repair!