Hegen go for 150. If breastfeeding go for slowest teat, even if expressing milk they also don’t need to size up as fast as compared to formula as bm is quite thin. I would get 1 Hegen and 1 of another brand. See which one baby can accept then can get 3-4 bottles so you don’t have to keep washing after every feed.
I won’t recommend to stock up on Hegen before trying as it’s very expensive. I got Hegen and Avent free gift, baby rejected Hegen.