Several improvements have been made regarding how labels are rendered within layout map items.
A new setting allows per-map control of how close labels are permitted to be placed to the map item's edges. Sizes can be set using mm/inches/pixels/etc, and data defined label margins are allowed.
A new setting allows per-map control of whether partial labels are visible in the map. This defaults to off, (unlike the canvas setting, which defaults to true for a new project) as layouts
should always default to the settings which produce the highest quality cartographic outputs.