Steep turn: do we need rudder once we rolled into a bank angle?
No.  You use the amount of rudder needed to keep the ball centered. No more no less.  Most of the rudder requirement is to correct for adverse yaw, and is only required while the aileron is being applied.
If you are in a steep turn, you may find you need to apply aileron out of the turn to hold the bank angle if the airplane has a tendency to &quot;overbank&quot;.  You might need to apply &quot;top rudder&quot; in this case, but only because adverse yaw from the top aileron will be making the nose yaw toward the turn and the top rudder is needed to align the tail with the nose in the airflow, to keep the ball centered.
The muscle memory activity that needs to be ingrained is left aileron, left rudder and right aileron, right rudder, depending on how bad the adverse yaw is, taking out the rudder input with the removal of the aileron input, with adjustments as required.  Your feet should just be squeezing this way or that way to center the ball, period.
Elevator/power (and aileron) is the only tool for altitude/attitude control in the turn (by &quot;and aileron&quot; I mean that once bank gets really steep, top aileron is often necessary to prevent the elevator application from just steepening the bank and tightening the turn - if you are targeting a 45 deg bank, this should be instinctive and you will be applying top aileron as required without thinking about it).
Use of &quot;top rudder&quot; rudder to prevent the nose from dropping, as opposed to just keeping the ball centered, is a cross control maneuver that results in a slipping turn (the ball will move to the low side), and if you stall out in a slipping turn, you will roll over the top as the outer wing stalls first and start to spin.  Many pilots have been killed by using &quot;top rudder&quot; as attitude control while turning to final and finished their lives right there.
I should also note that you can use a slipping turn to lose altitude on the turn to final, so you are in fact cross controlled with into turn aileron and top rudder, but this is a special altitude loss maneuver where you are making no attempt to maintain pitch attitude or altitude, just letting the nose fall through.  Done properly, there is no stall risk when doing a slipping turn (you aren't pulling and in fact you might actually push a bit), as can happen if doing a level steep turn.
So don't overthink it.  Just use your feet to keep the ball centered at all times unless you are side slipping on purpose, and get yourself into the automatic habit of squeezing left rudder with left aileron input and right rudder with right aileron input, and no rudder with no aileron input (but making applications as necessary if the ball drifts off).  A 172 needs very little rudder application to maintain a coordinated turn so it should just be little squeezes of rudder.
If you learn to fly gliders, where LOTs of rudder is needed to do the same thing, these actions become well ingrained because you have to, to get the damn thing to fly straight at all, which is why I always recommended learning to fly in gliders first.