Switching to full Formula

Hi mummies, Due to premie baby’s inability to suckle and latch properly and my low milk supply, i am Doing mixed feeding. Currently only 2 weeks into this and Am already on the verge of giving up as it can be really tiring. wondering if anyone can share their experience if any with purely formula fed infants? Do babies who are purely formula fed grow up to be less strong and intelligent? As much as I hope my milk supply and baby’s latching can be up to mark, it is really a drain on my energy so hope to hear some views! TIA!