Hi, Nickyb1982!
You can preview an effect without dropping it onto the timeline, for instance, in the PiP objects room you can view the superimpose effects before you add them to your video, just choose any one by clicking on it in the media library and watch how it behaves. If it souts your needs and the "mood" of your video, you simply pull it down onto the Video 2 track. Below that is the Particle room, again, click on the one you think might suit your video and view it whilst it's in the media library, if you like it, pull it onto the video 1 or video 2 track. these are not able to be made transparent, but there is an opacity setting you could attempt to set(I've not been able to get it to work, myself). I admit, I've not yet used any in my videos until I've had a chance to experiment with them. Above these is the effects room, these can also be viewed before inserting on the Effect(fx) track or superimpose directly onto the video clip on Video 1, 2 or other video tracks you can call up. If applied directly onto the video track, it will effect the entire duration of the clip(or highlighted portion) on any of the video tracks, but if inserted on the fx track, will only apply for the length of time you determine, and only apply to the Video 1 timeline. There's quite a bit of experimentation ahead for both of us, it seems. There are a lot of things I'm still learning about in PD14, but what I've told you here, is knowledge I've gained from experimentation done for the purpose of writing this post.
Cheers!
Neil.