Surely, I`d be glad to help you help me! (I have only a really old book as source, which makes it not exactly accurate)
Well, the horses are credited with the ability to walk over water and land with the same speed (which was twice the fastest horse in the land), ignoring climatic hazards, natural or magical, and were taller and stronger than normal horses, but not to a fantastical degree, and their vigour and health was normal. They also ignored illusions as if they weren`t there.
Manannán`s boars were bigger than a cow, many times stronger than a normal boar, being able to crush through wood and stone with ease but not exactly chaotic unless provoked. They also were credited with golden or silver skin and gave off intense light, even from their roasted meat. They always regenerated entirely as long as a single bone remained with marrow, though the comsumption of marrow slowed the regeneration process, which was one day if the bones were intact. They were eaten every year, and their flesh was able to expand the lives of men for one year with every consumption (while preserving the vigour of the time of consumption), and ten times that for Tuatha de Danann and other fey. They also remained perfectly calm and obedient in the presence of Manannán.
The poisonous boars that killed Diarmait were ravenous beasts that were full of spiky deathly poisonous fur, were as tall as trees and relatively strong (not nearly as strong as those described before, even though they were thrice (or more) bigger, but way stronger than a normal boar). They also roamed the land eating what they could and uprooting trees.