The source material doesn't actually tell us much about the Gall-Gaedil other than that they existed, sometimes killed other people and were sometimes killed by other people. Irish annals are generally terse texts (there are a couple of exceptions) where you're lucky to get any narrative descriptions beyond "so-and-so, son of so-and-so, made war against the some-such in this year." Descriptions of clothing, hairstyle, equipment etc. will generally be found only in narrative texts like the various mythological cycles, propagandistic texts, hagiographies and so on. And even then, outward descriptions of characters are usually entirely symbolic; characters in early Irish texts lack interiority, meaning that their personal qualities are reflected in the colour of clothes that they wear, the material their garb and equipment are made of, the colour and style of their hair and so on.

As for the Gall-Gaedil, we only have a couple of references to them in historical records. The Fragmentary Annals of Ireland for example only contains three entries out of hundreds that make reference to them, but those few examples are quite telling about the Gall-Gaedil as a general social-cultural entity:

856 Áed, king of Ailech, the king of greatest prowess in his time, gave battle to the fleet of the Gall-Gaedil (that is, they are Irish, and fosterchildren of the Norse, and sometimes they are even called Norsemen). Áed defeated them, and slaughtered the Gall-Gaedil, and Áed brought many heads away with him. And the Irish deserved that killing, for as the Norwegians acted, so they also acted.

Máel Sechlainn went to Munster, and he was at Imlech for a month, raiding Munster, so that he took the hostages of Munster from Comar Trí n-Uisce to Inis Tarbna in the west of Ireland. That was the battle of Carn Lugdach. In that battle Máel Cróin son of Muiredach, one of the two kings of the Déissi, was killed. Although Máel Sechlainn did not make this expedition to take the kingship of Munster for himself, it was worth coming in order to kill those Gall-Gaedil who were slain there, for they were men who had forsaken their baptism, and they used to be called Norsemen, for they had the customs of the Norse, and had been fostered by them, and though the original Norsemen were evil to the churches, these were much worse, these people, wherever in Ireland they were.

858 A victory by Cerball son of Dúnlang and Imar over the Gall-Gaedil in Ara Tíre.

So the Fragmentary Annals present us with a picture of the Gall-Gaedil as a pretty heterogeneous entity. They were a combination of Irishmen who appear to have taken up the "viking" way of life alongside some Scandinavian customs (and possibly adopted their beliefs or at least forsook their own) as well as Scandinavians who had been raised by Irish people through fosterage. Fosterage was an important institution in medieval Ireland where a family would send their sons or daughters to be raised by another family, with the purpose of solidifying political bonds between the two groups - it was a way for aristocrats to form alliances between one another without the use of dynastic marriages. This indicates that almost immediately after the Scandinavians had established themselves as a permanent force in Irish politics and warfare, many Irish aristocrats and their Norwegian and Danish counterparts made a clear effort to forge friendly diplomatic relationships and military alliances.

Were the Gall-Gaedil more Scandinavian or Irish? I don't think that it's possible to actually answer that question with any sort of certainty based on the evidence available. All we can say is that they were a distinct cultural and possibly social group (the annals don't tell us if they lived in Scandinavian settlements or formed their own communities) that were a heterogeneous mix of Irishmen who adopted Scandinavian customs on their own will and Scandinavians who had been raised and encultured in the households of Irish warrior-aristocrats and vice-versa.