Hi jasesun23,
There are all “best judgement” choices that you will need to make based on your budget and individual circumstances but “best practice” and what I would personally choose to do if I was building my own mattress would be to enclose all the foam layers inside a mattress cover that was specifically designed to be used for this purpose (see post #15 here) and then add a protector to protect the finished mattress. A mattress cover and a mattress protector are different products that have different purposes.
My previous reply includes links to more information and pictures about the effect of different types of covers on latex.
The better sources for mattress covers that I’m aware of are listed in the component post here.
Phoenix