Do muscular individuals automatically have a lower heart rate than less muscular individuals?

No, muscular individuals do not automatically have a lower heart rate than less muscular individuals. Whether heart rate is low or high has nothing to do with how muscular or ripped a person is, but rather with their cardiovascular fitness. So, you can be as muscular as you want, but if a skinnier person is more fitness-inclined, their heart rate will be lower than yours.