For product wise option for showing extra text you can use any metafield app and will required some liquid code modification for showing that text on page. let me know if you me to get it done, you can DM me for this.
You can open a file “product-template.liquid” and find with “product-form__input product-form__input–quantity”. You will locate to add your label. Like this screenshot: https://prnt.sc/12ontqj
If you can not do that, you can add me as a staff, I’ll check it for you. (my email: jones.evan137@gmail.com)