I do my intros in the morning so they are tired and only wanting to find a warm pouch to snuggle in. Once they are in the pouch I keep them on me all day...I either carry the pouch or tuck it into my shirt. They then go back to their own cages for the night. I do this for a good 2 days to make sure they are getting along. On the day I decide they are getting along just fine, I clean the entire cage they will share...Pressure wash the cage, wash ALL fleece & toys.... in the evening before they wake I tuck the pouch they are in into the cage so they can wake together in THEIR new cage.
The first night is usually a sleepless one. If you can have them in your room that first night, it'll be easier on you.
As far as arguements.... they all do it. You'll hear a psssttttt-ing noise or little squeaks....it's hard to explain unless you've heard it...but it's normal. They move/shift/step on eachother in the pouch as they try to get comfy...the one that is getting jostled around will pssstttt the other. You may even hear a little crabbing... at that I would kind of keep an eye on them to make sure it's just a little tussle and a fight isn't breaking out.
But odds are if they are getting along at intros and the daytime sleeping...you're gonna be just fine.