Kyushu Visit

Hello,
Please, some advice on an upcoming trip. We are flying to Fukuoka on Oct. 20 fora three to four week visit. We would like to buy passes before the price increase. We do not have a set itinerary but will spend the time in many parts of the Northern and Southern regions of Kyushu. Do you advise to purchase multiple regional passes for maximum flexibility of travel? Can we activate each pass when we need them? Or is it better to simply purchase tickets as we move between locations? Thank you for your assistance!