I have Dell 7040MT with i7-6700/HD530 and transcoding work OOTB on bare metal (DS918+, ARPL, DSM 7.1.1-42962 Update 1) with real serial number and mac.
You must have a real serial and mac BEFORE installing DSM, if you change them after installation, transcoding won't work, I haven't found a solution for this.
You can't use DS3622xs+ for HW transcoding: