German here, and I like Aldi and Lidl. Edeka is great but also pricey. The demographics depend mostly on the area rather than the store itself, and the stores are nothing like the Walmart or Sam's Club I've been to in Mexico City. My first time at Walmart, I legitimately got nauseous. I'm a German outnumbered by roaches, slavs, blacks and jeets in the Ruhr metropolis, but I can assure you Lidl in a nicer district in Mülheim is German boomer central "morgens halb 10 in Deutschland" lmao, whereas Lidl in Altenessen was Mekka, Essen main station is swarming with 30yo wagies stressed to catch their train, and Lidl in my shitty hometown is empoverished Multikulti. The closer a store is to a bus/tram station, the more boomers you will find.
I've been to good and bad Penny stores, good and bad Aldi (North; South looks fancier), Rewe is always ok, Edeka is best but lacking in the store brand product offerings for poorfags like me.
Lidl is a good allrounder and had a tendency to be my favorite when I compared store brand products such as mozzarella or camembert in regards to pricing, ingredients/nutrition and taste. Their app is less spyware than other stores'. Freshness and availability of veggies can be hit or miss, but it's generally better than Penny or, god forbid, Netto.