Forget the first note for a moment. The D,F,Ab and Bb fall nicely under thumb, index, middle and ring fingers.You then have to move the right hand along, left to right, parallel to the way the music sheet is on the piano.At the same time, the thumb will be moving under the hand, in order to play the next D, and so on.Now, the first Bb. It really doesn't matter whether it's played with the ring, as it will be as you ascend, or the index or middle. I prefer middle to start, as it gives a little more space underneath for the thumb to hit the D.
On the way down. you start with top Bb using ring, and use up all the digits, and do the same lateral movement, right to left, though, as you did before. Again, the lowest, last Bb can be played with whatever you like.If you were going down another octave, it'd need to be played using ring, but as the last note, it doesn't make any difference. It's a scale - not as if you're going anywhere after it.
Your third idea is not so great. Generally scales come down backwards from the way they're played going up.Try not to flick your elbow up, or raise your wrist too much, more of a smooth transition of thumb under, whilst moving your hand/wrist/forearm steadily from side to side, going either up or down.