Ok, think may have found a fix to change slider caption without having posts or pages appearing on front page
Create a post for each slider you want displayed. Set title, text and featured image in each post.
Create a new page (not a post). Give the page a title like “Invisible”, and leave text field empty. Save the page. Go to Appearance > Customise > Static Front Page, and select “Static Page”, and, under the dropdown “Front Page”, select the new page you have just created, i.e. Invisible.
Now go back and edit Invisible, and delete its title, so that both the title field and the text field are empty. Update.
Now go back to the customise screen and in the “Front Page” dropdown you should see something like “#166(no title)” as being selected. Leave this setting, save everything/exit and check your site. You should now only see the slider image with the caption and text you have written in each associated post. Something like this for example: https://www.integrityorm.com/
Hope that helps!