Glad to help. Responsive Lightbox is a good gallery, lightbox and media folders plugin. dFactory isn’t super pushy with the premium/paid like a lot of plugins today. I use their cookie notice plugin too.
Regarding the WP admin bar, I typically turn that off in my profile so site is rendered as visitors will see it. I have Admin open in adjacent tab anyway. In the v5.6 test wordpress site I tried, the Lightbox completely filled the client window so there was no interference with the #swipebox-close button.
You can override the style #swipebox-close { top: 0 } to top:32px or whatever you want. I hope you are using a child theme, which makes overrides easy. Inspect the elements and add some overrides. Just be aware of multiple devices / media queries so any overrides perform as desired on different devices. I typically extract out the exact media queries from the parent theme and paste them (empty) in child theme style.css so any overrides can be constructed to use same media breakpoints/rules as the theme.
Have a great day!