Which cloud to learn?
Everyday you'll find people arguing about which one is better online.
Checkout job listings in your area and pick the one with the most results. PICK ONE AND STICK WITH IT. The fundamentals are the same and our advice is the same.
Are paid cloud learning platforms worth it?
These do help you avoid spending your own money in your own AWS and Azure accounts, which when you're getting started is a good thing. Ultimately, if you sign up for one, it's up to you.
I (GPS) had a subscription to A Cloud Guru and Linux Academy when I was getting started, my work paid for it though, maybe this is a perk your work can pay for too.