Hardware recommendation

Glistening noob here. Making a robot that I want to do object detection and tracking on. I think I’d like to use a raspberry pi due to budget requirements. I tried to do some OpenCV tutorials using my RPI0 and was surprised at the result, very, very slow. Before investing in more hardware, I wanted to know is real-time object tracking going to work on a more powerful RPi at a reasonable frame rate such as 30fps or more? Will it matter if I get the 8GB ram RPi4 version? What would you recommend for a budget application?