Antietam battlefield is well worth a visit—very interesting site, and easier to grasp than Gettysburg. Of course it is a smaller battlefield than Gettysburg.
I concur with you about the Antietam battlefield. One can walk the entire battlefield in a single day’s visit. It has been several years since I was last there, but then the visitor’s center was quite good.
Here is a link to a pdf copy of the Army’s Center of Military History “Staff Ride” book on the battle. I consider it a ‘must have’ when visiting the battlefield. I know the author and he is an expert on the Battle of Antietam and led dozens of staff rides to it for the Army staff and other military groups. He has since retired from CMH.
https://history.army.mil/html/books/035/35-3-1/cmhPub_35-3-1.pdf