Pinnacle 16 vs Pinnacle 16 Plus
Keyframeable effects means that you can set values for the effects at various points along the timeline.  For example, you could tell a dissolve that you want to start at 100% opacity, then move to 50% opacity 5 frames in and then sit at 50% for 20 frames and then dissolve the rest of the way to 0% by another frames.  The effect will make sure it hits each value on the frame you specify and blend the values automatically to get to that value.

Without having it, you should probably still have frame accurate control, but you'll only have a begin and end point to work with, no control over how it progresses in between those points.  It's a nice feature to have, but shouldn't be critical for your described purpose.

Chromakey would seem to indicate that you can do your titles in either, but you may have to produce the title in an image editing program outside of it.  I'd guess that it will let you do static titles inside the program, but it sounds like it won't let you easily make the title move without going to the Plus version.