Love hot sauce! I started making my own as a hobby years back, every year the peppers commandeer more and more room in the greenhouse. So far my favorite varieties for making hot sauce are the super versatile basket of fire peppers, habenero, Carolina reapers, and scotch bonnets. I find habenero and basket of fire peppers add really nice flavor with good heat, while Carolina reapers ect really boost the heat levels.
I like to typically make three different kinds every year. A sweet heat type for those who find milk spicy, a nice and hot type, and then a super hot type that is basically abuse. This year my reapers didn't make it, which was dissapointing but I had lots of habeneros of different varieties so was still happy.
I find over time the hot sauces lose a little heat, but more flavor comes out. Typically I use mild peppers 50/50 with hot varieties to make up base. I prefer Anaheim peppers for this, but bell peppers work well too.