Hi heavysleeper2009,
Welcome to the Mattress Forum! 
Yes, the 2 lb density would be preferred to the 1.8 lb for someone of a higher BMI, but for the short term (1-2 years) I wouldn’t be as concerned regarding the durability. The UD Eurotop does have two more inches of polyfoam in the core and as you mentioned the upper panel is exchangeable, but if you think that you respond well to a “typical” firmer mattress (remember Dreamfoam’s scale starts with firm at a 1 and soft at a 10), you may choose to go with a more “basic” configuration of a “firmer” UD Latex mattress with a configuration around a “3-4” or whatever they might recommend in a phone call. The difference would come down to your personal preference of the ability to customize, which it sounds like you’re “comfortable” without having that option.
FYI, post #3 here has more information and suggestions about heavier weights that is worth reading.
I’ll be interested in learning of the results of any phone conversations you may have with Dreamfoam, and any decisions that you might make.
Phoenix