As you know VNAV will compute it's own speed reduction point ,going from 250 kts to flaps up speed at that point.If you'll select Vnav before this point,the target speed will become 250.
FCTM recommends to select VNAV aprox 2NM before FAF (if you've used other pitch mode).
You can force the 210 kts on the FMC by selecting restriction on different waypoints or by making it the target speed,but generally it's not required.
If you fly an unrestricted vnav app,the method is to use lnav with whatever pitch mode you feel required,and 2 NM before FAF select VNAV with MDA on the MCP.Procedure it's the same for 737 classic or NG.