Ireland has PR but it's PR in each individual constituency so it doesn't just go by country wide vote share. There is sometimes a discussion on how the country wide vote related to the no of seats. One particular party were very good at managing their vote share to deliver more seats. Parties very occasionally get an overall majority, sometimes propped up by independents in a manner not unlike Theresa May's deal with the DUP, and more recently we had a minority government propped up by the second largest party. We have had so many coalitions and they decide on a programme for government before agreeing to go into government and then aim to deliver that. So there are compromises made there.
Our constituencies are multiparty constituencies and we have a single transferable vote so you might actually get 4 or 5 TDs all of whom you have a vote to. How this works is all the votes are counted and TDs have to reach the quota (total no of votes divided by no of seats available) to be elected. Once someone is elected their surplus is redistributed proportionally to the next candidates down the list. Same if someone is eliminated. So you could vote for say the monster raving loony party as ypur no 1, safe in the knowledge they won't get in and your no 2 will be counted instead. If your no 2 gets elected with a huge majority, your no 3 will be counted and so on. So the larger parties run 2 candidates or 3 and sometimes get all 3 in, though that has become rare of late.
Our 2 largest parties are aligned along civil war lines and not on a really strong left/right division so fondly known as two cheeks of the same arsenal and indeed formed the last government together (still needing the Greens to form a majority) rotating the position of Taoiseach (our PM). But that is a very very recent development, for years we just swapped from one to the other, sometimes with other parties, sometimes not. It used to often be Labour being the minor party in coalition, it's just as likely to be the Greens more recently. Labour got burned same way as the LDs, the minor parties often do as they get in as a protest or floating voters who can't bring themselves to vote for either of the main two. We've also had the rise of Sinn Féin, mainly a protest but nobody would consider them as a coalition partner so they are the largest party in opposition at the moment. I don't think they will do as well in the next election. Plenty of smaller left wing parties but we were missing a smaller right wing party, as they propped up the Celtic Tiger government for years so got decimated when the bubble burst. We do have a Sinn Féin splinter group, I suppose they are right wing socially but I don't know if I'd say they are economically, I tend to tune them out.
I think people vote differently under PR. It's not as simple as your x in a box though of course you can just give your no 1 and not fill in any of the other boxes. There are parties I would never give a vote to no matter what.
A lot of things still apply to us like choosing candidates over party or party over candidate, which a lot do and editing to add a lower share of the country wide vote can still mean a much higher share of the seats, and a higher share of the vote doesn't mean a huge number of seats for smaller parties either. It is very constituency dependent. Sometimes there is nobody actually running in my constituency I particularly want to vote for, so I still have to do the least worst option.
At the moment we do have a real mix in the Ðáil (parliament) but we have had PR since the foundation of the state and it's been stable over all. It is interesting at the moment because of the relative collapse of the civil war divide, but in the recent elections for European Parliament and the local elections/councils those two parties still got most of the seats and votes.