Hi TheFriskyFairy,
Welcome to the Mattress Forum!
Having a high BMI presents special challenges and generally requires firmer materials (in the support layers especially). This could be firmer latex or innersprings (the type of support component would be a personal preference and in the right design either could be suitable) or even a zoned construction. The same overall guidelines apply with higher weights though that PPP (Posture and alignment, Pressure relief, and Personal preferences) along with using high quality durable materials that will maintain their feel and performance for longer periods of time are the way to make the best choices. Heavier people in general will need firmer and thicker comfort layers and firmer support layers than those who are lighter and because no materials will last as long with much higher weights the quality and durability of the materials and components is even more important than normal. I wouldn’t “rule out” any types of mattress and base your choices on your own personal testing. Post #3 here has more information and suggestions about higher BMIs that is worth reading.
The key will be finding componentry that will be of appropriate quality for your specific situation, which will then give you the best chance at have a successful comfort life, so I would always make sure that you find out information listed here so you can compare the quality of the materials and components. Those in a higher BMI range want to be especially prudent in the choice of their components. For those in a higher BMI range, there is more information about selecting a mattress in the durability guidelines here. As you spend quite a bit of tie in your bed sitting and laying and are not gentle on it, be sure to follow the higher BMI guidelines and you may wish to look for something using a firmer edge reinforcement system as well. And don’t forget to browse through the mattress shopping tutorial for overall guidance of how to select a mattress.
Phoenix