Firstly, thanks for sharing the solution of your issue and for your suggestion about showing derivation paths. Already discussed, not implemented yet, though.
Secondly, as for the documentation, you are absolutely right, we have been working on it but there is still a lot to be covered. Trezor Suite is a new app, more detailed manual is about to come. So far, there is some basic information Suite manual:Receiving payments - Trezor Wiki
As for receiving Ethereum, simply create ETH account the same way you added your ETH Classic account. When you have your ETH account, use its receiving address to receive ETH and ERC20 tokens. One ETH account can receive ETH and multiple ERC20 tokens, meaning you don’t need to generate for each token a new ETH account/address.
As for other apps, you can use Trezor with any compatible app you like. See them listed https://wiki.trezor.io/Apps. MyEtherWallet is also an option. By using the same seed (stored on your Trezor device) and the same passphrase (if enabled and used) you will be always given the same list of accounts and addresses no matter what app is used with Trezor.