Choosing between fixed CPM and flexible CPM depends on how much control is needed and how the campaign is set up. Fixed CPM means you pay the same price for every thousand impressions, no matter what. This helps with planning your budget and knowing what to expect. Flexible CPM adjusts the price based on competition and performance. It can be cheaper during low demand and more expensive when demand rises, but it also gives a chance to get better placements during good times. Some use fixed CPM to keep things steady, while others prefer flexible CPM to make better use of changing traffic. Has anyone tried both options and compared the results?