In the album, track, or merch editor, under the pricing section, you’ll see “Payments will go to”, followed by an email address. If more than one payment address isn't available, the artist will need to first list their unique PayPal address on their Profile page. Listing the artist's PayPal account here will not override any label settings; only the label will be able to make edits on a per-release basis as described above.
Items set to pay a label will appear on both the label and artist accounts, while artist-paid items will only be visible on the artist page. Only the current payment recipient can edit payment details.