Hello,
Thank you for contacting Rank Math and apologies for any inconvenience that might have been caused due to that.
Can you please confirm you are using Rank Math FAQ Block in Gutenberg? If so, You can change the title from the FAQ Block settings. By default, the titles are set to H3.

In order to change the answer paragraph text size, add the following CSS rules to your theme’s style.css file or use the Additional CSS option available under Appearance > Customize inside your WordPress admin area.
#rank-math-faq .rank-math-answer{
font-size: 10px; /* Change the font size as you want */
}
Hope that helps.
Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.