I run four and sometimes more trains using a 6627 transformer. everything seems to run fine except smoke units on steam engines. Does the 6627 have enough power to meet my needs?

Hi Jerry
The 6627 transformer is a 30VA transformer (blue case) reliable but not suitable for later Märklin models (today's analogue / degital locos) as you may fry the elctronoics (decoder) when sending a reverse oversoltage.
This transfo is perfectly fine for older (electro-mechanical) as those between the 50s and the 80s.
At the time there were two motor sizes and many locos could run on a 16 VA transformer while the "Deluxe" models required more power and a 30 VA transfor like yours.
These were conservative measures by Märklin as you may have lighted trains, smoke and switch control.
Big speech (sorry) to say that running 4 locos SIMULTANEOUSLY with ONE transformer is optimistic and is even worse when the smoke unit is installed.
- one motor power need 10 to 20 VA depending on the model
- very old and large 800 series locos 30 VA (e.g.: CCS800, DL800, ST800, G800)
- a CONVENTIONAL (not pulsed) smoke unit takes an additional 8 VA

NOTE: don't run smoke units without fluid as they heat-up and get destroyed

Cheers
Jean