unhomogenized goat milk was the most agreeable but i could never get dairy digestion to the level i wanted it and i suspect the connection between thyroid and dairy intolerance being the cause for myself. this was after trying whole milk, skim, a2, "lactose free" a2, unhomogenized goat milk, etc
the protein in goat milk tends to be more agreeable (doesn't produce β-casomorphin-7) which can have an impact on digestion, but this doesn't really matter that much as you can just drink a2 cow milk. some posit that goat milk having smaller sized fat globules makes for easier digestion.
for myself, trying every milk variation looking for the solution was a bit of cope when the fundamental issue is thyroid it seems. if you address that and dairy digestion becomes agreeable, you can't go wrong with rays recommendation of skim or low fat milk, anything without fortified vitamins or other nasties should work nicely.
my own TSH has been trending upwards for some years now (the top end of the reference range for normal limits is comically high). ray i believe said for a healthy person TSH should be below 1 and anything above that is a sign there could be impaired metabolic health. pulse is important in this context as well because there are other factors that can suppress TSH so you need to check other markers to get a good picture here of your metabolism.