Dominant is always expressed when present. Recessive is only expressed when no dominant genes are present.
The main difference between autosomal and X-linked is that autosomal inheritance is the inheritance of traits that are determined by the genes in the autosome whereas X-linked inheritance is the inheritance of traits determined by the genes in one of the sex chromosomes
our genes constitute only about 2% of our DNA. Most of the DNA in which we may be identical is noncoding DNA, not our genes.
But even aside from that point, if all of us have 99.99% identical DNA, the other 0.01% still leaves more than 3 million base pairs in which we differ, which leaves a lot of room for human variation.
Dominant is always expressed when present. Recessive is only expressed when no dominant genes are present.