The tax set up screen will be skipped if you already have a tax rule defined in the eCart object. If the tax is already set in the eCart object, it does not need to be reset when running the checkout wizard.
The screen for configuring the email receipt will only display if:
1) Universal Email or CSS Form builder 2 are installed
2) You select to use a local checkout method.
using a remote checkout method, the gateway will handle sending the email receipt.