The maximum level (ie, no sink rate) turn you can do with 6G Wing Loading is 80.4 Degrees.
The turn rate will be dependent on the velocity of the aircraft.
With a 9G Wing Loading, a 83.7 Degree Level Turn.
I suspect at exactly 90 Degrees, most airframes will have a tendency to yaw towards the ground and would be a handfull to fly....
As for bank angle in a sustained turn. Its dependent on the wing loading and wing loading only.... The rate of turn is dependent on the wing loading, bank angle and airspeed....
Example a:
Say a 1 ton (1000KG) airplane is flying at 450 knots and has a maximum sustianable wing loading of 6G and wants to perform a sustained turn..
Figures:
Speed, 450 knots = 225 m/s
Max G = 6G
Maximum sustain bank angle 90 - (sine X) ^1 x 1/6 = 80.40
F=(Mv^2)/r => 22300r=1000(50625) => r =2270m i.e. implies turn rate of 6 degrees per second.
At 225 knots (ie 112.5 m/s) radius will be = 567 m turn rate will be 11.7 degres persecond
For a 9 G turn at 150 knots(75 m/s) turn radius will be 200 m, turn rate will be 22.5 degrees...
For a aerobatic plane such as a extra 300 at 75 knots doing a 9 G turn level turn , turn radius will be 50 m..turn rate will be 43 degress per second......Things are starting to get high here now....hehe