All of the aforementioned styles (and others) are still available. What you need to use depends on what you want to heat. Easier starting? Look for oil surface heaters (dipstick, oil pan blanket, in pan element) Warmth in the cab? Look for coolant heaters (freeze plug, in-line heater hose). Using either type will heat the other liquid a small amount by thermal conduction.
I think (in my area) using both types connected to one source plug is the way to go, though I'm too lazy to set it up on my rig. If you live in extremely cold areas (winter Alaska, high in the Rockies) heaters are basically required equipment.
I use a good, clean coolant, mixed to -75degree rating, no heaters.