To send a standard text rather than a message through Messages/iMessage on a per-message basis, just do the following on your iPhone:
Tap and hold on the message you want to send as a text. From the pop-up menu, select "Send as Text Message".
Note: Sending a message to a non-Apple device will always be sent as a text, at least unless the other user has an Apple messages compatible app running (unlikely as of 2023).
I usually write a blog post about once a week. The latest post can be viewed here: What Is Anything?: Use language in an honest way to communicate instead of obfuscating. (posted 2025-08-07 at 20:27:52). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-07-18 Too Many Road Cones: I think it is clear, there are too many road cones!.