One of the traps in adding text to video is you cannot make QUALITY EVALUATIONS based on the Canvas window on the computer screen.
If you do, you can end up making the wrong creative/corrective decisions.
You need to view the FCP output on an external video monitor (NTSC or PAL, depending on where you are) to check motion and/or quality of a FCP image or graphic DURING the edit (this is how FCP is designed).
The better the quality of the monitor, the better you can judge the levels, color and resolution of the edit… but in a pinch ANY outboard monitor will show you how the actual motion will appear and relative sharpness of the image you’re working with.
This is a must for making these evaluations on any project that will be output to tape or DVD.
As to specifics of titles on a DV timeline:
https://www.creativecow.net/articles/hodgetts_philip/titles/index.html
https://www.kenstone.net/fcp_homepage/perfect_titles_phil.html