3 billion bp in a haploid human genome, 6 billion in a full diploid one. If you store the masked/unknown/variable ranges as annotations on the side, you can get away with close to 2 bits per base, as you suggested.

The axolotl haploid genome is 32 Gbp, which, in 2-bit encoding and ignoring masked bases, takes 8GB to store.

Axolotl, like humans, is diploid, meaning it has 2 copies of each chromosome.

That’s only about 10 times the size of the human genome. That being said, the complexity of a genome doesn’t scale with size. Many plant genomes are gargantuan but highly repetitive. The Kolmogorov complexity of a genome would better predict the complexity of the organism than a genome’s length would.