This is the first of their CPUs. The iMac will almost certainly be running a higher end CPU which at the very least supports more RAM. It's likely the 16" MacBook Pro and the higher end 13" MacBook Pro will share a CPU with the iMac the same way the Mac mini and the MacBook Air share a CPU.
For replacing the Xeon-W in the Mac Pro and iMac Pro, they will also need a higher performing CPU, sure.
The 16" MacBook Pro is only available with a discrete GPU, which I don't need but causes me tons of issues with heat and fan noise. The dGPU has to be enabled to run external monitors, and due to an implementation detail, the memory clocks always run at full tilt when the resolution of driven monitors doesn't match, resulting at a constant 20W power draw even while idle.