Always appreciate your analysis.
First thing that sticks out to me about Schaefer is his skating. We are talking about Makar, Quinn, Orr level skating here.
Second thing is his vision and judgement while carrying the puck. Seems to make the right move or pass more often than not. Creative, but seems very efficient in his moves, which should wear well in the NHL.
Haven't watched him enough to comment on his puck retrievals, but if they are as good as you say, that's a huge bonus, as I think it's a highly underrated skill for Dmen.
His main weakness appears to be his defending basic line rushes, but that is common with offensively inclined Dmen, as they tend to play the puck rather than the man, as it allows them to go the other way if they can poach the puck. IMO, it's a pretty easy fix to make him better in this regard, especially for a guy with his combo of size/length, and skating. I guess his shot needs to get better, but his ability to find shooting lanes is notable.
Unlike Hughes and Makar, Schaefer already has good size. Remains to be seen how strong he will get, but i am guessing he will be above league average for a Dman once he fills out.
This is high praise, but he looks like Bobby Orr out there. Much more imposing physically than Makar and Hughes during their draft years. I was going to mention Coffey, who was also a great skater with good strength, but Coffey was the 4th Dman taken in his draft year(hard to believe).