The increased severity over generations in Huntington’s disease is known as anticipation, common in trinucleotide repeat disorders, so not super relevant to the “wobbly morphs”, which as far as we know do not show a trend of worsening with subsequent generations. So a large part of the difference in HD is just number of CAG repeats. Although we have found a good number of genetic disease modifiers (papers coming soon - stay tuned!)
Have you read through the thread on allelic morphs? Allelic Morphs aka Complexes [Ball Pythons] A lot of this has already been covered/explored/discussed in great detail