[eurg]

This was a nice overview, and I basically concur.

I want to add a few things.

Once you know your grinder, too high a max pressure is not so much of a problem, as choking a shot becomes a rare issue.

Consistently good Espresso is easier using a slightly coarse ground, but something needs to give, like texture or concentration.

Taken together, cheap machines can work well, although learning on them can be frustrating.

Use fresh roasts, and use them up quickly. Some days after opening a bag of not single dose frozen beans , many coffees lose their good aroma, and only the roast itself remains.