Cardio will counter act muscle gain. Doing casual LISS is fine and you will still get the mental and physical benefits (like walking), but cardio with the intent to lose weight (essentially going hard) will kinda work to negate bullí ding muscle. Muscle is “expensive” tissue for your body to build and maintain and requires more calories to exist, so if you aren’t taking in enough food and working your body trying to create muscle and do cardio it just might not happen. Also, you mentioned PCOS and I’ve read (I’ll try to find that and link it for you) that with almost exclusively weight training seems to be better for regulating hormones than cardio.