Feature tests shine when they assert HTTP outcomes: status codes, session flashes, and database side effects. Reach for actingAs() when you need an authenticated user, and keep factories focused on the minimum attributes each scenario requires.
Aim for one clear behavior per test. If a case needs three unrelated assertions, split it—future you will see the failure line and know exactly what regressed.
Run the suite on every push; the cost is small compared to shipping a broken registration or payment flow.