So, upfront CTF cost is gone. For developers in Apple's Small Business Program, there is a 0% 'acquisition fee', 5% commission (and if you ship on the App Store or use IAP, that bumps to 10%), +5% Core Technology Commission. Total 15%, same as today

If you're distributing outside the App Store, and you're in the SBS, somehow you've got to give Apple 5% of your app revenue.

If you're not in the SBS, you pay a 2% acquisition fee on all transactions, 13% commission to exist, +5% CTC. Total 20%

If you're using the External Link entitlement, you must use Apple's API for linking out (so they can track you), and your transactions are also subject to a +5% Core Technology Commission.

(Total commission using external links: 15% for small business program, 20% for everybody else)

I think, based on my read of this, that if you're a small developer on the App Store (and can qualify for the SBS), and want to also provide your apps on an external storefront with some other payment service, your total commission will be 10%, but with no way of Apple tracking that I expect you'll be self-reporting your revenue for them.

Apple retains audit rights for all developers in the EU under these terms.

There is a long table explaining what the difference between Tier 1 and Tier 2 is. If you choose to pay the reduced store services rate, you lose: expedited app review, automatic updates, school/business store, you only show in App Store search for an exact match, no user reviews, no in-app events, no recommendations, you will never be featured by Editorial, have no access to promo codes, and no analytics. It really is a stripped-down version of App Store hosting

https://developer.apple.com/help/app-store-connect/reference/store-services-tiers