Yes, an ISP could see that you're using a lot of traffic. But if the traffic is encrypted, they can't be sure what you're doing. Are you a personal user? Or are you a business? How would they know if it's all encrypted?

As for the volume of traffic you're sending, you need to read the terms of your ISP contract, at least a little. Your ISP could have volume limits (e.g. only 5TB of traffic per month), and if you reach those limits, they could temporarily suspend service. But if they can't see what you're doing, and you're within the technical and contractual limits of your service agreement, and you're not causing problems for them, then an ISP is not going to care what you do.