I didn’t tried the cage free, we have a topic where many strings get reviewed by our dear @theendofcake.
In here you find so many reviews, I not always agree with they but usually there are good points to start to understand some strings.
At the beginning also the difference in strings is probably hard to feel, I just directioned you to something very good that makes everything less frustrating and durable in time.
Also 100% polyester is just a type of string, a material (which is also the ones I use usually) but there are so many mixed materials like nylon, poly and nylon etc etc (will not worry at the moment about those different ones)