I’m currently about to purchase a cot for my seven month old baby however I have some concerns about her hitting her head on the wooden slats or getting her head stuck as she moves a lot currently in her bassinet I’ve heard of cot bumpers however I’ve also heard positive and negative about them how they’re unsafe. What do you recommend?

Firstly Red Nose recommends that once a baby is rolling they need to be moved to a cot from their bassinet. Baby needs their arms free (no swaddling) & the space of a cot to roll well & safely.
Rolling usually occurs by 4-5mths of age. https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

Hopefully, you have now bought the cot. Many babies will wriggle, squirm & move about a lot in a bassinet - often due to not having the space to roll. Once she is in her cot you may find she may/may not hit the sides or get stuck. Injury is very rare.
Red Nose does not recommend the use of anything soft or padded (including bumpers) in the cot.
https://rednose.org.au/article/baby-products-you-dont-need
https://rednose.org.au/article/at-what-age-can-i-introduce-cot-bumpers-and-pillows