Yaarel
🇮🇱 🇺🇦 He-Mage
For me, a player giving a genuinely good argument or rousing speech means giving an advantage to the check.The issue with the rp first approach in dnd is that I can act out a rousing speech, that stirs the emotions and ought to persuade the listeners and then the DM calls fir a roll and it fails. My RP is meaningless because of arbitary chance.
Also, the story is considered before any mechanics might happen. Mechanics is only if there is doubt that something might or might not happen.
So, if your plan really is so solid that it there is no real doubt that your plan would work, then it simply does. There is no need to roll a check in that situation.