A reel at 104 with some shuffle emphasis might sound great. The same tune with evenly picked notes might have to be a lot faster to feel right. Another characteristic of traditional Celtic styles is ornamentation. Some of the ornaments used by players of other instruments are difficult or impossible on the guitar. Ornaments are not requirements.
Many tunes sound great without any.
But a little carefully placed ornamentation can often bring out the flavor of a tune. First-string grace notes are usually the most comfortable but they can be done on any string. In Irish music the single grace note is usually one note in the scale above the melody note. In Scottish music you might grace with a larger interval. This can give a bagpipe feel to a tune.