Guild Wars 2

If I have 1 other person in my party, will the matchmaking pair my party of 2 against a full party team, another party of 2 and 3 pugs, or other party combination?

What if my party has 3 people instead? I rarely queue with a party of 4.

The opposing team can have any number of premade groups. Matchmaking does not consider premade groups at all. The only exception is if all 5ppl on 1team are solo que they will never face a 5man Premade. Using you examples of a duo que.
Yes you can face a 5man premade
Yes you can face a 4man +1 solo
Yes you can face a 3man + 2solo or another 2man
etc.
Hopefully this clears up your question.

You and whoever is in your party will always get put in the same match together. As for filling the rest of you team it’s just random and can be a mix of solo/duo/trio players in the queue. Same deal with a party of 3, the game will fill you open spots with a duo or solo player.

I am asking about the opposing team. I meant to ask if the system will match us against a similar team composition or just automatically match us against a full party team.

A full party team (could be anything from 5 man premade to all solo queue or anything in between). Party Comp is not taken into consideration. That’s a total crap shoot. I’ve been in matches with a balanced comp on both sides and I’ve been in matches where my team was 4 reapers + 1 DH and the other team was 3 Ele’s + 2 Thief, and even other’s where between the 2 teams we had 8 necros…

I was not talking about party comp. in term of classes. For example, would a group of 3-man premade and 2 pugs be fighting against a 5 man premade group?

It’s random as to what you’ll get. So yes, you could be against a 5 man premade or 5 solo queues, or a 2-premade and 3 solo queues…. all depends on who has queued up in the system