Agricola’s ships circumnavigated Britain, probably also did the same with Ireland, and he planned to move the provincial capital to Chester, and to conquer Ireland. Apparently he made a reconnaissance in force (probably of short duration) and built a fortified trading post on a peninsula north of Dublin.
His appointment as provincial governor was extended because he had such big plans and was effective, reliable, and loyal.
Overall, his campaign in Caledonia probably led to the overall success of Roman Britain, the Picts and Irish enjoyed the benefits of trade. There were a couple of times Roman direct rule was extended to the Antonine Wall, but there really wasn’t much of any value in Caledonia or Hibernia, and the Romans had other things to worry about. The last campaign was by Septimius Severus, whose dynasty collapsed after his death, and that collapse helped usher in the Crisis of the Third Century.
The Scots were an Irish tribe that didn’t cross into Scotland until the Romans had been gone from Britain for about a century.
The Scandinavian Vikings swarmed all over the British Isles throughout the Middle Ages, with the final victory in 1066, when Viking descendant William the Conqueror / the Usurper / the Bastard (he was called all three of those, still is) destroyed the last of the Anglo-Saxon nobility.