You've probably noticed that in some of my cards, I specify general traits for the user (such as gender, age, or a brief backstory). I do this for a couple of reasons:
First, it significantly improves the quality of the LLM's responses and the overall roleplay experience.
Second, I thoroughly think through the lore and plot of each card and design the bot's behavior around them. The bot performs best under these specified conditions. However, if you don't like the provided user description for any reason, you can easily change it yourself by editing a few words in the bot's definition (I usually place the user's description at the very end of the card to make it easy to edit).
In short: Don't worry, the user persona built into the card always has lower priority. If you have your own persona selected and active, it will automatically override any default user description in the card. The card's built-in description only acts as a fallback when no persona is chosen, so it won't interfere with your custom persona at all. I've tested this myself, so there shouldn't be any issues. I hope this clears up any doubts! Feel free to roleplay as you usually do - the user description in the card won't get in the way of your adventures. :3