Grind settings are widely different for each bean, it’s normal. Depends on a lot of factors (origin, variety, altitude, roast etc).
Lighter roasts tend to need slightly longer ratios (~1:2.5 to ~1:3.5), darker roasts shorter ratios (~1:2). Faster shots (20-25s) are usually fine.
As for channeling issues, puck prep is of paramount importance but I’m not sure how much prep you can introduce in this machine’s workflow. Counterintuitively, channeling is often caused by grinding too fine, but the water rushing in the channels actually make the shot much faster. If you can WDT between grinding and tamping, it would solve a lot of issues.