Sigplus is not behaving the way I expect it to in J!4, so let's see what happens here in J!3...
First thing I'm noticing is that the sigplus-edit-button (in the backend editor) is showing up nicely here. In J!4 there's no button, but an appearance in the "CMS" dropdown.
What I want to check, though, is whether Sigplus will display a Flickr album. Yep. No problem.
The underlying markup/styling for Sigplus is surprisingly lean - which means the layout can be customized with just a few line of CSS.