As a rule the fingers being used should have enough curl in them so the joints even up the fingertips in other words level. There is a certain falacy that the hand needs to change angle to level out the finger tips, or use the longer finger to play 1st or 2nd string so you do not have to stretch so much with the other finger etc..
Truth is when the correct amount of curl is used, then the fingertips will be level.
If you can learn to swing from the middle knuckle, rather than the large first one ( from the wrist ) then you will find a better angle of attack because it is steeper going in between the strings and coming out. When we swing from the large knuckle, especially with straighter fingers, the arc is flatter and the tendency is to brush strings either side as the fingers go in and out between the strings. Sometimes the nail will catch the string because the shallow attack needs the tops of the fingers or it will catch the string to thick or sometimes even trap the finger from coming out smooth.
As for tucking in the fingers not being used, i say tuck them in, as it gives the playing finger better momentum, especially if it is the fore and middle finger playing and the ring and little finger tucked in. In a regular hand, just tucking in the little finger will bring the ring finger on with it. As a learning aid to teach the hand how to do this, simply hold a pick or a small coin in the crook of the little finger and that will bring in the ring finger.
Bear in mind depending on the health of the hand, results will vary at the start but the long term results will basically be the same for all.
Floating thumb or fixed anchor? Floating thumb gives the wrist a better postition to play because of the reduced angle over fixed anchor. In floating thumb the hand is flatter to the strings so the wrist angle is straighter. In fixed anchor ( or any of the thumb anchor positions ) the thumb is behind the fingers as a rule so the wrist arches back to the strings to allow the fingers to reach them. depending on the bass and the height etc, this will vary, but as a rule floating thumb has a straighter wrist position than fixed.
Consider the elbow as important as the wrist in helping the wrist find its position, a bad elbow position can put extra bend into the wrist, and a good one can take some out.
As usual we all have different ranges of motion due to our lives and health, but these are just a few of the more beneficial areas to look in helping you hands stay healthy and improve technique.