Took that cruise last year and loved it. I did not make it a beer cruise, but would recommend the following:
The Weltenburg Abbey excusion -- Weltenburg is the oldest operating abbey brewery. The church in the Abbey is unbelievable.
Fruh brewery and the Gaffel brewery in Koln (Cologne). Be...
Man Reaches Age Where He Carefully Checks ABV% On Every Beer He Drinks
https://babylonbee.com/news/man-reaches-age-where-he-carefully-checks-abv-on-every-beer-he-drinks
In addition, if you are buying kits, the grain milling may not all be the same. the finer the grain is milled, the better efficiency. I mill my own grain, so my mash efficiency is pretty consistent from batch to batch.