You can install PlayStore apps from the App Lounge which connects anonymously. Most apps simply work, always depends on what you use. Apps such as Plexus or Sapio can be used to see if apps work

N26 works in my siede and others as well. Always depends on the bank. You can find a curated list here: https://community.e.foundation/t/list-banking-apps-on-e-os/33091

I use /e/OS on my Fairphone 3+ since more than 3 years and can only recommend it!