Sorry if this will seem harsh/nit picking, but you asked for what the eye sees, and for me about proper use of equipment and figures.
First, I do like there is a lightly tensed line/steady connection, that the circle is relatively the same, and even the tempo is the consistent (albeit too fast). And I like the horse.
As to equipment: side reins are supposed to be attached approximately the height of the rider's knee (or a straight line from horse's mouth to horse's point of hip). They are NOT to enforce longitudinal flexion nor to close the throat latch, but rather to allow the horse to 'meet a steady connection' and offer a little even bend laterally. By doing so, if the horse is properly laterally flexed (a smidge on the circle) it will develop a connection with the outside rein (which straightens the horse and forms a basis for riding as well (horse up/open/lightly itv). Hence they are really only met for trot because in walk/canter the horse needs to bascule/telescope within the gait.
When side reins are attached by the elbows the mouth is torqued l/r as the moves, so it articially lowers and closes (the throat latch). But NOTE that the horse is flexing at the THIRD VERTEBRAE, which is incorrect. The horse will alway ground its forefeet where the nose points, if it is btv the horse will ground there.
There is a big difference between running forward and active. Remember SPEED is the ENEMY of IMPULSION. Yes, one can get longer strides by rushing the horse but the shoulders will drop because the hindquarters end up only pushing the load. First relaxation and swinging, then amplitude/length. Otherwise the hocks suffer. Likely when the s.r. are set so low the handler HAS to chase the horse to keep it going, and what 'yields'? The middle of the neck.
Half halts should be employed while lunging to fold the hind legs/slow the horse's tempo (if needed) and to FOLD the hind leg joints so they articulate and carry with energy.
Ideally too the work would be with the line to a caveson. If it is over the top the hh should serve a purpose which is lowering/opening.