I read into this back when I shucked my first HDDs. At least for external drives the 3.3V rail is used as a reset pin. If it's pulled high the system won't register the drive. I'd use a Molex to SATA adapter personally instead of the tape trick.
In terms of HDD cache, more cache can really help the random read/write performance that's common in desktop applications, gaming, and datacenter workloads. 32, 64, and 128 MB is pretty common on desktop drives (or older high-end drives) and are good amounts to have. 256 MB is more common on high-end/high capacity drives, and it's really important for SMR drives as their write performance can be quite low. Currently, there is only a single drive with 512 MB, the WD Ultrastar HC550. I would stay away from "cheapo" HDDs that are like 1TB in capacity with 8 MB of cache though--I think those are often used by OEMs to hit 1TB for the lowest price possible, which results in abysmal system responsiveness (looking at you, PS4 Pro). SSHDs can come with several gigabytes of NAND cache in addition to DRAM, though the flash will wear out over time.