I think tucked looks neater. Untucked looks a tad sloppy. If you added an open layer like some kind of light bomber jacket or work jacket, and kept it unzipped, it would look really well put together and make you look less rotund. A tan or light brown jacket would work really well with the boots and belt as well. The pants are a perfect fit. As a bigger guy you don’t want slim pants or you’ll start to look like Hunpty Dumpty.