hopefully nothing got damaged after your fill procedure and being potentially the wrong level. The proper procedure is, with the car level, to fill with the engine off until it's running out of the hole, then have someone start the car and slowly go between reverse and drive a few times while you continue to fill it until it runs out again, then you put the plug back in the fill hole, leave it running and let it warm up to to 40
C or 104F then check the fill hole again, let it drain out until it's just dribbling or add more as needed.
Here's a link to the procedure I used:
ZF 6HP26 drain and fill
As for the trans fluid I used Ravenol 6HP fluid as it's cheaper than any OEM fluid but still designed specifically for the ZF trans. bmw’s, jaguars, benzs, rolls royce might not use OEM Hyundai fluid but I'm sure Hyundai's specific fluid is identical to all the other manufacturer's brands of trans fluid, most OEM's dont make their own fluids anyways, it's just a rebranding of an oil company's fluid. It's up to you as to what fluid you want to use and I'm sure some non-ZF specific fluids will work just fine, but personally I like to use something that's designed specifically for my application.