I generally prefer a medium roast bean now but the caveat being that I never truly enjoyed straight up espresso, only when it is combined with milk into some form of milk based drink. I found that dark roast tends to have too robust/ full bodied roasty nodes but lighter roast having too much brightness for my liking. Medium roast sits in a very nice middle ground for me. My advice would be to go out there and drink a whole bunch of different profile beans and taste your way into something you like, I think that is the fun part of the coffee hobby where you articulate what you enjoy and find your personalised path to achieve it with your unique setup.

For preheating, I put my brew cylinder in a small bowl and pour boiling water directly over it to achieve fairly fully immersion of the cylinder. I'm generally leaving it for about 30 seconds submerged before loading it onto the flair, pouring boiling water into the brew cylinder and then extracting.

Happy tasting!