About half and half. The reg section covers stuff that applies to FEs, W&B and meteorology will be the same. But there are a lot of systems questions - Heat and centrifugal force on turbine blades causes: galling, creeping or streching. What tread wear will occur if tires are underinflated? What causes a surge of current when incandescent lamps or electric heaters are first turned on? What is the purpose of a reverse current relay? How are cylinders numbered in a double row radial engine? (you didn't say which test you're thinking about.)
And there will be some questions figuring power settings or dump time or fuel burn or specific range.
The rule is a little bit different than the ATP written rule but it just says you have to be hired by a 121 or 135 in the 24 month window and you have to be employed by one when you take the checkride.
When you take the test it's through CATS or LaserGrade so you're hooked to the whole FAA question bank. Sheppard Air has a good record for doing training.