When it comes to standard
titles, you're free to use/not use any combination of settings on the Title Designer's Object tab.
The same goes for the Effects tab
with the exception that you can only use a Special Effect (from the Object tab)
or the animations on the Effects tab (which has been renamed to Animation in PD19), not both. As you found out, backdrops also conflict with the animated Effects and will be disabled if you choose to use one.
If you'd like to fade in/out a clip with a backdrop, you can drag a fade transition onto the start & end of a title on the timeline or simply keyframe the opacity up and down from 0 to 100 then back to 0.
For more context - there are reduced settings in 3D titles and for add-on packs like Motion Graphics and Minimalist Titles, and in all cases you can only work with the tools and effects provided by the Title Designer.
If you have the New Blue Titler Pro plug-in, it has many more degrees of freedom and styles of available effects than PD's titles.
For
regular photos and video clips, up to 7 different FX can be applied en masse or indivdually to any single clip, and all the other Fix / Enhance tools can be used as well. Only a single CLUT or Color Preset can be applied to any clip.