I don't think you will notice a speed difference.
Unsure about swapping the cables straight over, and the H/d working.
My own was a clean install on the Epox 9NPA+ Ultra, and the drive was automatically detected.
The biggest benefit I have noticed, is in the performance of my two optical drives, as both are now set as master, on their own IDE channel.
I don't think it would cause any harm, by switching your drive from IDE, to SATA, and see if it boots as normal.
Also check the bios settings, to see if your first boot device, has a setting for this.