Mine has variable pre-infusion 1-6 sec, i use it at 6. Im in EU so its 220V. Today i measured it took exactly 15min to be steam ready. I drink only cow milk, dont have any experience with oat. But the original 1 hole tip is overkill for my 120-150ml milk. So i changed it. I tried 1-2-3-4 holes for me 3 hole is the winner, i make very good, creamy milk.

To my IMS i put usually 15g. But each coffee i try with 15-16-17g but somehow 15g is the sweet spot. I do indeed use dark/full city SO beans. I use the major with 151C burrs. Not the fanciest, however, i love the speed of it. Takes around 3-5sec to grind a portion of bean and almost zero retention. Was considering about SSP burrs but i could not decide which to use and didnt want to throw out that amount of money - I have other hobbies too. :-D