The text I've added is cut

The amount of text that can be displayed in a title slide or caption depends on the theme you chose.
We recommend keeping texts as short as possible: people do not watch videos to read!

Use the preview before exporting, to check that all your text is there. If text shows too small or is cut off, the best way to fix it is to place shorter text, either by reducing the text or splitting the text on multiple text slides. 

Customising texts it not always an available option: text font, color or position can be changed with the video theme Raw, a Pro video theme.

Note that 360p and 720p are different resolutions and the text may appear differently from one version to the other because the pixels don't take the same space in one case and the other.