These components were aligned to work with the best possible performance in conjunction with low power consumption and quiet operation.
GPU: In all cases the GPU is soldered on the system board and cannot be exchanged.
CPU: The CPU is in almost all cases "socketed" which means the CPU is removable from the system board, which does not mean that the part should be exchanged/upgraded or modified by the customer.
A replacement of that system core component only will be made during a repair in an authorized service center if the component is defective and needs to be replaced. In a case of a defective CPU, it will be replaced with the same part and not with a higher type.