Establishing breastfeeding can be difficult but once you are past the clusterfeeding and have a good latch and supply it is much easier than FF.
Expressing was just an extra hassle and DS hated the bottle, I can't imagine having to make up bottles at the right temperature etc to feed on demand, you'll no doubt have a hungry baby crying in the night, have to go downstairs, prep the bottle etc and all while trying to comfort the baby compared with pick up the baby and breastfeed.
The first requirement is determination, nearly everyone can breastfeed if they just persevere, yes there are times when you feel like you have done nothing but feed all day, and it can be painful particularly if there are problems such as tongue tie or simply a shallow latch but it gets better particularly helpful to have good support.
I had to be very strong as I had a lot of negativity from in laws regarding breastfeeding and also DH was worried about the pain I was experiencing initially and had also been influenced by his parents views however soon became my biggest champion!
I found it helpful to educate myself on normal behaviour of breastfed behaviour, as FF is very very different and so many people will tell you that baby must not be getting enough etc when it wasn't true at all.
When establishing supply the worst thing you can do is start topping up with formula as your body wont know baby needs extra, over time with a lot of combi feeding the amount of formula goes up, the amount of bf goes down which leads to a downward spiral and your milk supply will "dry up".
What makes you thing you wont be able to breastfeed 24/7 Pens?
xx