Normally, transitions apply only to adjacent clips on the same track, and higher tracks always take precedence. But fades can cross tracks.
Like this, where boy fades to dog and back again...

That said, transitions between tracks can be programmed in Multicam mode. Right-click the preview window, choose Preview Mode | Multicam.
Or there may be a Multicam button to launch the feature...
Experiment.
Changing a clip or adjacent clip's length may remove a transition, so it can be best to add transitions between fully edited adjacent clips. Effects 'stick' - normally they won't change.
Multiple sequences can be embedded into a single track. At the top-left of the bin click the Sequences tab. Drag the desired sequence to the target track, or right-click and choose one of the placement options. These embeds are composites - not individual clips - and should be edited prior to main track insertion.
Building in levels, with individual exports to be later assembled, is one approach. Building sequences for insertion into the main track is an alternative.
Consider adding narration last, to the main sequence. Narration tracks can be positioned at will.
You are limited to available effects, but your adjusted settings for each can be saved as a template. Click the blue icon
and name it. That customized effect appears at the bottom of the effects window, to be applied to other clips.
Bin clips can be sized prior to timeline insertion. 
A master bin clip can be duplicated numerous times. Right-click | COPY. Then in an open area of the bin right-click | PASTE CLIP.
Edit each copy for unique IN/OUT points. That won't affect the other copies or the master.
When done, select the desired clip and drop it into the timeline - perhaps at the cursor, using the right-click placement option.
In general...
Use the 64-bit release.
Prior to the start of a new project, go to OPTIONS | DISK tab and Clear Unused Cache Files. (This can also be done while editing.)
Don't import clips to the bin that won't be used in the project.
For protection, Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, that choice is available by clicking the caret to the right of the Save Project button on the toolbar. Saves will restore the project via a double-click on their VPJ file.