"Mirrors"

The city start has only been improved; everything has been built to level 2, and each hero has 3 stacks. Given experience with scenarios with much worse starting conditions, special preparation is not necessary; it is more important to practice on a template, which is individual for each player. It is better to simply add 1 subjective restart to be able to reroll the "unliked city" or an unpleasant layout. I also don't think there is a need for trading for heroes, because the heroes should be of the same class, and for example, in Castle, one will take Caitlin, and the other will be left with garbage.

No. The gameplay for some castles has noticeably changed in HotA. Tyrus with the Citadel, Flax with a guaranteed Moon, Necropolis through Lords, Inferno through new Magogs – I won't even mention the Conflux. These are all very significant things that need to be practiced deliberately so as not to give the opponent an advantage. It is quite difficult to train all of this well in a couple of weeks. And a restart does not guarantee that the castle will change. However, 1 subjective restart, regardless of this, is also a good idea, in my opinion.

What does it mean that the heroes should be of the same class? Are you willing to give up all 10,000 starting gold for the Moon? No? Then there are competitors, and you will negotiate. And if you leave everything to the will of randomness, then the Moon will periodically come for free and sway the balance much more noticeably.

P.S. The question of why Katya is relevant to Castle is a good one. Castle offers the most balanced start in terms of heroes. Valya stands out a little, but again, it is easily balanced by trading.