Hi jasesun23,
If a layer of latex is inside a mattress cover/ticking (that is made to be used as a mattress cover) that surrounds all the materials and components inside the mattress then the individual layers don’t need to be encased but if you are using a latex layer as a topper on top of a mattress then it’s generally a good idea to use a dedicated cover around the latex topper in addition to any mattress protector you are using (see post #2 here).
Based on your descriptions of the Ikea mattress pads they would both probably have a bigger effect on the feel and performance of a mattress than one of the thinner membrane type protectors (and they wouldn’t be water resistant or waterproof).
Phoenix