The sweep-picking technique has no limit when it comes to arpeggios. The common shape is usually considered to be the one with two-octave stacked triad, or the one in scalar terms which is also the first (tonic), the third (median) or even the fifth (dominant) of a scale. It is played twice with the help of an addition first (tonic) added when the shape is at its highest point. When the series of notes are pulled fast, an arpeggio is formed. They are mostly used in the blues-based progressions.
Alternate picking is not mostly used in this form of picking, even though many shredders prefer it. A legato can be used though, so that that the sounds of the notes can be heard when you are picking them. However, hammer-ons and pull-offs are mostly preferred whenever you are trying to do an arpeggio. Mostly, in the upper and lower sections of an arpeggio, you will use strokes on the same string and it will create a natural sweep-picking motion for you. This is mostly used when one string has to make a sound for two different notes when you are using a natural shape in a guitar.
However, you have to make sure that when you are playing the arpeggio, you are doing it in your own style. That is what makes you different from other guitar players. Therefore, some guitarists may use the legato, while the other would want to double-pick different notes on the same string. It is a different idea and many use it even though others don’t prefer it. The sounds will be different, and the notes used will be different as well.
Most players also master this technique by using the sweep picking technique. You can perform a lick, like most guitarists do. It is still better than alternate picking and considered to be a more technical idea as compared to alternate picking.