We adopted a 6 month old and an 18 month old at the same time. It was very very full on for quite a while as we had two babies who were strangers to us, in nappies, competing for attention, grieving, traumatised etc etc, whilst trying to be these amazing therapeutic parents, responding to each kids needs immediately etc! It really was quite exhausting, although it was also an amazing and lovely time ( in between nappy changes!)
When they were toddlers the level of night time (and daytime) nonsense was pretty high! Nothing traumatic, just giggling, mucking about etc which tested my patience. Also, with teething, feeding, insecurities etc, we definitely had a lot less sleep than ideally I would have liked! They clung quite quickly to me, rather than my partner and needed a lot of 'me' which was quite draining and hard- but also quite a privilege.
They are now 5 and 6 and are great fun, great pals (when they are not poking, hitting or nipping at each other). I feel like we probably have it easier than people parenting only children as they amuse each other no end! I do wonder what parents of 'only children' shout at their kids for though, as the main source of irritation in our house is sibling squabbles!!
I can't really undersell how fraught and stressful parts of the first year or so was- we funnelled a lot, responded to their needs, did a lot if carrying which was physically hard, adoption in general is emotionally hard, but there was lots of good times, the kids are amazing and funny and settled and great. So wouldn't change it for the world.
They both draw a lot of comfort from the other and I believe their relationship is the main protective factor for them. They get so much confidence from each other and they really are very much a team! I love watching their relationship with each other and they learn so much from each other, it's quite amazing!
Good luck!