I went on my own sole trip to Reims following an RS Best of Paris. I had some knowledge of Reims' offerings, but while walking --and visiting the helpful/accessible near Cathedral and a fine restaurant---I discovered Reims. Spent 2-3 days there.
Went to Pommery tour, which was art-filled cellars beyond amazing.
As a fervent Catholic & educator, the Cathedral was my #1.
Got a taxi from the TI to the museum in which Germany signed surrender papers to US Army officers (right near train station). People there were excited an American visited & sought me out during my self tour so I could attend their surrender film.
Reims is very walkable. In fact, I walked w/luggage from my hotel to the train station on my way to CDG airport.