I have used 2 different machines for foaming. I've found that the more pressure in the steam wand, the more consistent the micro foam. For instance, in my HX, at 1 Bar, I found that it was challenging to have the same quality of micro-foam at the end of the pour as in the beginning. Even with polishing. At 1.4 bar, it was better. Newer machines up that to 2 bar, but things happen very fast and one's technique needs to be better. (I've never used 2bar) The very fussy quality of the micro-foam is not evident until you start pouring various designs of latte art. It's easier to do tulips with foam that has a bit too much air, but if you want those lower 'leaves' to wrap around, then the foam has to be thinner and more consistent to get the white foam to swim more fluidly. Latte art has much stricter demands on the consistency of foam (and your crema has to be solid to act as the base)
More foam makes the drink taste good, while too little foam (hot milk) tastes terrible and so I always err on the side of too much air and thus it often kills any good latte art I hope to do. I often bail out in mid-pour to the 'heart'.