the part where it has 2 gears is a nice identifiable confirmation that yea, it's got 2 gears haha, 2 speed! cool! They work okwith ATF too vs ND30. the detergent oils should be fine, only really an issue with the rubber parts. the detergent is meant to keep dirt suspended so that it can get pulled out in an oil filter, which this doesnt have, so ND is ideally better but people have run 10-30 or 20-40 with good results. some people find ATF gives better grab, though I would prefer more slip to engage higher.
That all said, without personally experiencing, ND30 is pretty easy to come by so that'd be my goto. ND20 is available from tractor supply places and many folks claim it rides better. Pretty easy to swap - if you really care, the best is always tuning it by feel yourself - try it, change it, try again. You can always let someone tell you something but when theres alotta different answers htats usally cuz it comes down to personal preference!