The various arpeggio types that you can select from are listed on page 81.
Note that some of them were designed for specific types of voices, such as "guitar arpeggios" or "percussion arpeggios," but you can still use any arpeggio type with any voice, although the results can vary from extremely interesting to extremely weird depending on the arpeggio and the voice.
For instance, I used to enjoy picking a "sound effects" voice, such as a laugh, picking a percussion arpeggio, adding a lot of heavy reverb or sustain or other voice parameter changes, and fiddling with the tempo until I got some pretty "satisfyingly weird" results.
This was on my PSR-E400 models, which have some features that the PSR-E300 models don't have, such as the ability to modify a voice's attack/release and cutoff/resonance settings from the control panel and function menu.
The PSR-E300 have those parameters, too, but to access them you need to connect to an iPad or computer and use MIDI software, such as Yamaha's Sound Controller app for the iPad, iPhone, and iPod touch.