Do integrated graphics make the CPU slower?
Not by a large amount but slightly. Integrated graphics use the system resources as they are embedded into the motherboard. It shares the CPU memory and clock time thereby putting a slight strain on the system resources. It also induces heat inside the CPU  in the long run which slightly affects the performance of the system. Running a graphic-intensive game with iGPU would slow down the system as it’d use the system bus more thereby consuming more CPU resources and causing lags. But if we compare all the pros and cons of an iGPU, it has more pros than cons. iGPU gives an overall boost to the user experience and doesn’t drain a lot of battery.