Paced feeding is very important.
When baby gets milk it comes out slowly and only comes out via stimulation, which is the innate suckling action babies do which they have to do as it's biologically ingrained, it's so that they build supply during growth spurts.
So when you feed a bottle it comes out quickly and it's too much at one time, it's not what would naturally happen. This can stretch the gut leading to gut issues and mental health issues given the gut microbiome is a huge part of the gut/brain axis.
So either paced feed, which is a pain and I did not have the patience myself, instead I got a Mimjumi bottle which mimics the breast and released milk slowly and only on suckling.
It was a godsend. After formula my girl seemed so bloated and red and even in pain. I was combi-feeding as I got no latch, so primarily she got expressed breastmilk and so I was able to note a palpable difference.
I used to give the formula at night as it made her sleep through, which is not good really because they are not meant to sleep through, they have to wake, again to build supply and to know they are safe and regulate their heartbeat.
So the way we feed can be really detrimental and stretch the gut and distress the baby, whose tiny stomach is too full from a whole bottle at a time.
I think feeding on demand is a great idea because it mimics nature. I did this too, I did not just give a proscribed amount of milk at a time, I've seen people do this and the baby kicks their legs, they are basically being force fed and you can see after they are in pain, that's the gut being stretched.
I would definitely recommend the Mimjumi bottle. I would do that over paced feeding, which is really taxing, the bottle just does it for you.