how fast a car/how fast is this car

[Vladv1]

How fast a car is this / How fast is this car? How reliable is the man?/ How realiable a man is he?
Do those pairs mean the same? Which construction is more preferable and natural?

 

[Tarheel]

"How fast is this car?" is more natural, but the other one is possible.

"How reliable is he?" is most natural, but the others are possible.

 

[jutfrank]

Do those pairs mean the same?

Yes.

Which construction is more preferable and natural?

Neither is more natural. Neither is more preferable in itself.

 

[emsr2d2]

1a. How fast a car is this?
1b. How fast is this car?

2a. How reliable is the man?
2b. How realiable reliable a man is he?

Always number sentences!

Do those pairs the "a" and "b" options in each one mean the same? Which construction is more preferable and natural?

Something can't be "more preferable".