The extraterrestrials are clearly able to “return” an individual to nearly the same exact moment in time with no physical changes when they have been part of a “20 and Back” tour of duty in service to the Secret Space Program, but all kinds of deep subconscious changes happen. I assume they could just as easily return instead, the full 20-year physically aged version of the individual as well (not that they would, except for “fun” on rare occasions) and retaining their entire 20 years of memory, or even the physically-aged individual but with their memory of the 20 years wiped? (I can imagine the PANIC of waking up 20 years older and looking in the mirror!). Are these options nothing more than a kind of calibration change in their time travel technology?

This is actually the case that both scenarios are quite easy to produce depending on the need for the time travel in the first place. So the reason, in the first instance, for the "20 and Back" program is to compress the training of an individual and their service into what appears to be no time at all from the standpoint of the self taken from their ordinary life and then returned to it seamlessly as though no time had gone by at all when, in fact, they have been elsewhere for 20 years and doing things at the behest of the Extraterrestrial Alliance. So this shows the tremendous reach they have to manipulate things. They could as easily return someone from the end of their 20‑year tour and bring them back to the moment they may have been taken as a child and age‑progressed, even before starting the tour itself. So there are a number of scenarios, and all that you mentioned can be done. It is a question of the need at hand and how it will serve the Extraterrestrial Alliance. They do not do things for effect. They do things for purposes that are deadly serious and fully in alignment with their own selfish goals. They do not care about the consequences for the humans they manipulate.