1. is Astra's yearly license similar to GeneratePress where you get the pro addons for lifetime but only get the updates and support for a year, or does all pro features get taken away after the yearly license.
2. Are the prebuilt website options the same with free and pro? If so do you only get more options with the agency package?
3. Is the agency package worth the extra money over pro?
4. Is the more modern features and direction with astra worth the switch from generatepress?
So to answer your questions:
1. Yes, you only need to renew if you want support and future updates. There is also a renewal discount.
2. Yes, they are the same, Astra Starter Sites. There are others that are solely in the Agency plan, but some of those require the included plugins in the Agency plan.
3. I think so, but it mostly revolves around if you will find value in the included plugins with are, Ultimate Addons for Elementor & Beaver Builder, Schema Pro, Convert Pro, and WP Portfolio. Also the premium website designs and any new plugins they as a company sell.
4. I think so, for my needs. Also Astra has integrations with 3rd party plugins, something that GeneratePress doesn't have.
All that being said, GeneratePress is fantastic. I am not urging you or anyone to stop using it.