This guy is pretty much me.
>Pretty bad but not ridiculous
You could live in NI through the troubles and be entirely unaffected by them beyond hearing the conflict mentioned. Even some parts of Belfast went relatively untouched.
There were several key areas which were shitholes full of constant fuckery from one side or the other, the most famous of which being Divis Flats.
In these areas, and areas around them, you had to be careful what you said, where you went and when, how you carried yourself; all it took was for you to be in the wrong place at the wrong time and you were fugged.
British soldiers got it hard; some of them weren't paddy-slapping bastards who were just doing what they were told, but in the eyes of the nationalists and IRA all brit soldiers=murdering scum.
On the other hand, if you were irish or catholic you were essentially memeraided in your home fucking constantly by the very, very, very anti-irish police force along with the army while they checked for guns or whatever.
Protestant Paramilitaries sprung up too, largely because they wanted in on the banter of shitting on Irish people and all of sudden Irish nationalists or catholics had 3 armed forces to avoid.
tl;dr-Where it was bad, it was baddddd but for the most part it wasn't hellish, mostly just a bit shit with a few serious skirmishes here and there.
>How effective
Like he said, it depends. Bombings were a very mixed bag; a well placed one was very effective but many of them were just placed near at random in unionist areas in order to fuck their shit up.
The irish paramilitaries were infiltrated constantly by Britfags so they had a strict secrecy rule which, if breached, meant very bad news for you.
To sum it all up, user, don't image a city engaged in all out war.
Imagine some shitty skirmishes on a street, car bombs, people getting stabbed or shot in parks and pubs, people vanishing, and constant police raids.