Hind leg angle needs to be the same as the front leg angle.
The angle of the front and hind legs needs to be parallel.
Be sure that the hind legs are as elevated as the front legs in your mediums and extended trot. The angle of the front and hind legs needs to be parallel as in the diagram.
Us dressage judges are taught a judge training sessions to penalise movements where the angle is not parallel, so please don't be surprised or indeed disappointed if you don't get the mark you were expecting when a flashy and elevated front end is not matched behind.
So for paces I look for freedom, regularity (rhythm), length of stride and foot flight. A horse that tracks up nicely tells me that the hind leg is coming under and carrying a good amount of weight promoting self carriage. This in itself ticks a big box BUT if the front feet are a elevated by a good foot and the hind feet are dragging on the surface then marks will be affected.
So it's a powerful and engaging hind leg that propels the body forwards energetically forwards and through. If this is achieved then you'll give yourself every chance of some stunning work!!