You can use both! Salicylic acid works more for unclogging the pores and glycolic acid works for renewing the layer of your skin. Just be sure to use sunscreen during the day because the glycolic acid will make your skin more sensitive to the sun.

I would use your salicylic acid during the day followed by an SPF moisturizer. Use your glycolic acid during the night followed by an moisturizer unless your using an aha lotion then no need for moisturizer.

Using one right after the other can cause irritation making acne look worse. So, use the bha during the day and the aha at night.

Mandelic acid is a great option as its a two in one. It acts like a bha and aha. It's very strong and I only use it once or twice a week. I use a 5% mandelic acid toner from muac.