Yes the difference in steam power between the Oscar and 6910/Classic is enormous.* I have 2 steam tips for mine: a 4-hole tip for entertaining and a 2-hole tip for daily use.* I find it difficult to get good microfoam with the 4 hole tip if doing less than 200ml of milk; just way too much steam power for my skill level.
I wouldn’t go adjusting valves.* Keep playing with your grind until the pour looks good; the correct grind for one machine is not going to the correct grind for another.* If the taste is good too then you have no need to play around with these things.* Don’t take offence but it doesn’t sound like you have any expertise in this area.* From personal experience, amateurish fiddling with these things can create more problems!
From my understanding the Oscar does not have an adjustable OPV anyway, but could be wrong there.
I noticed from your sig you have a coretto.* Do you have a flexible probe that could fit into the group handle?* You could check your temperature that way to see if the boiler pressure is too high and make adjustments.