Hey @edo888,
Your call, but this small change will add a “cool factor” to your plugin’s settings page (back end):
.postbox {border-radius: 10px!important}
Result? –> https://prnt.sc/FsV9kJpazrn5 🙂
The above CSS Rule affects all WordPress postboxes in the back end (still, a nice change). You may have to identify and/or create another CSS selector that will only affect your plugin.
Cheerio!