Internet required for poe camera

What internet speed us required for cameras. I currently have 2 stick up elite poe cameras. It often buffers for awhile or I lose the picture. I have 10/10 mps. Please advise. Second question if I get a splitter for my modem. I understand you are using the capacity of one port on the modem split into the splitter’s ports. Does having multiple cameras overload(for lack of better term) the modem or is it ok since I would only be viewing 1 camera at a time. Please advise. I will be purchasing another 4-5 cameras and would like to plan on purchasing a splitter beforehand