I played and wrote feedback for this game during Brackeys Jam, so now focusing only on your feedback questions:
Understandability: Gameplay is mostly easy to understand, but having to hover on the environmental elements to know what they are is a bit unintuitive, probably because the text doesn't show up immediately.
Difficulty: Took me 4 times to beat even though I played this before in the Brackeys Jam. You really have to understand those environmental elements if you want to beat the game. At first, they seem like hindrances, but there's a few ways you can use them to your advantage.
Difficulty variation: Some runs felt impossible, others felt much easier. Since your cards, the storms and the environmental elements are all randomized, I think this is bound to happen. This often happens in roguelikes and other games with randomly/procedurally generated content.
Following changes: This was confusing at first, but I got used to it. When I placed a card next to a swamp, and it effected other cards, I think those effects should have happened first, before the swamp moved the card.
Overall it has clearly improved from the Brackeys Jam version, even though the original version was already very good!