It doesn’t matter if you use the DNS of your ISP or not they can always see what websites you visit. What they cannot see is website contents if the website is using https, which most modern websites are.
That means your ISP can see that you went to youtube.com but they can’t tell which video you watched or what else you did on the website.
The only thing they could do is analyze the traffic and see that there are many requests in a short time and assume you are probably watching a video.
Edit:
They will of course also not see if you clicked on a category on 9gag.
Also there’s no reason for using a VPN as the VPN provider will see the exact same thing as your ISP.
It doesn’t matter if you use the DNS of your ISP or not they can always see what websites you visit. What they cannot see is website contents if the website is using https, which most modern websites are.
That means your ISP can see that you went to youtube.com but they can’t tell which video you watched or what else you did on the website.
The only thing they could do is analyze the traffic and see that there are many requests in a short time and assume you are probably watching a video.
Edit:
They will of course also not see if you clicked on a category on 9gag.
Also there’s no reason for using a VPN as the VPN provider will see the exact same thing as your ISP.