There is a pretty big range - but it ends up being a nice mix of large, medium and small. Large distributors will typically be your macro beer and liquor brands. Mom and pop distributors will typically be niche wine distributors.
A handful of chains have developed systems to create PO's, but a majority just rely on sales reps to service the account.
How does Walmart/Costco/Big grocery store chain place orders for liquor now?