Can my internet provider see my activity if I use stuff like brave or opera browser???
Your ISP gives you a unique IP address that identifies your device on the internet. By tracking this IP address, they can see which websites you visit. 
Yeah, your ISP can still see what you’re up to online even if you’re using Brave or Opera.
These browsers have privacy stuff like blocking ads and stopping trackers, but they don’t hide all your internet traffic.