What is the difference between a Scot and a Pict?

The Picts, whose name translates as "painted ones", were a Celtic tribe who inhabited most of Scotland from the Highlands to Hadrian's Wall, before the coming of the Scots, Britons, and Angles. The 3rd century Roman historian Eumenius described this tribe as "fierce and skilled in battle".

The Scots, who came to Argyllshire from Ireland in the mid-4th century, converted to Christianity around the 6th century. Although the Picts and Scots originally were allies in their skirmishes with the Romans, by the 9th century, the Scots had absorbed and assimilated the Picts. By the 10th century, this co-mingled group together with Britons and Angles would make up the ancestry of today's Scots.

The ethnic heritage of the Picts is not fully understood.The Picts spoke a Celtic language.Some scholars think they were originally a people related to Basques or a different non-Celtic ethnicity that became assimilated by intermarriage into Celtic culture.The Scots were Celts

Picts seem to have been earlier settlers.

No difference, they just share the misfortune that they were both invent and re-invented by the Romans and Bede.