Have I looked at Sunlu S2, yes, here is a recent post on that topic that may provide some insights and methodologies to overcome some of the shortcomings in dryer technology.
The one hint I will share with you that my writeup only touches upon. Humidity sensors are practically worthless. My findings were that there just isn’t a consumer level product that can be trusted. Weight is the only truly reliable way of measuring moisture reduction. But as was recently point out to me by a fellow forum member, if you have a cardboard spool, even weight is thrown off substantially due to the spool itself becoming a source of moisture. This is yet another reason I prefer plastic spools. That said, I am taking the plunge and will be constructing a respooler precisely so that I can respool cardboard onto plastic and therefor eliminate cardboard as a factor in drying.