Yes you can. But you have to know the Outside IP for the Gateway the NAS is connected to. Along with the proper ports setup to allow outside connections through the use of the utility for that NAS. Majority of the time the problem you will run into, is that the Upload speed is going to kill trying to open or transfer large files.
When I first got my Lenov ix2-4 NAS. My brother and I played around with the Lenovo software to see what kind of issues we would have. The software is just pure garbage. He got better speeds by setting up on his machine a remote server share connection to it.
When you connect to a personal NAS and assigned a "Sticky" DHCP IP for the Modem/Gateway, you would use the "Broadband" IP to connect to your home network. You then are asked for the login credentials. The only time a "Sticky" IP will change, is if you swap out the modem or Gateway.
You need to know also, that there are providers that will block certain ports to stop file sharing, or if they see a lot of traffic to a person's IP, they will only leave the ports for Web Browsing (80, 8080) and mail ports.
You really need to decide in what option you want. Just remember that if you put all of your eggs in the same basket (ie only use the NAS at your home), if it crashes or the house burns down. You lose everything saved on that NAS. That is why a lot of us use redundant copies of the data (local, two remote clouds on different providers, copy of highly important data on a USB stick and on a DVD, kept in a fire safe or off site).