Richard William's Animator's Survival Guide talks about the distribution of weight in a character's walk cycle at length, and through his observations, it sticks out whenever a part of a character remains uncannily stable when the whole of the body is hustling.
That three-quarters angle at the start, is a really ambitious full bodied shot- and it's done really well here in mannequin form- everything reads. But what isn't translating as well as it could is the twisting happening as the shoulders rotate opposite of the hips. You can get by with making the shoulder circles be wherever, but it's going to be a completely different feat on a full-bodied character, with specifics to anatomy and clothes. You already know this, but the twist is going to be a difficult facet of animation to master.
My eyes are also drawn to the positional relativity to the head. You look at an actual runner/a person running in real life, and the head bobs and weaves, swaying side to side as weight transfers between the feet. The point between the eyes, if looking from the front, should draw a "U" or a curved bowl shape. Sometimes even a mobius strip depending on what's going on at the hips and shoulders.
What I'm seeing here in these tests are a lot of steadycam heads- they're all horizontally stable for the most part. And take that critique with a grain of salt; lots of animations do it, and stylistically that works to comedic effect, or budget-conserving measures in cartoons.
IF you're striving for a more realistic stride, use live models for reference. Even if it means looking at yourself in a mirror, recording a friend, or having a friend record you. Even the top-budget animation studios will film live models performing the desired action- not even to rotoscope them, but to have live reference. If they're doing it, to great success, you can do it too. If there's a voice of doubt or anxiety decrying that as cheating, you can rest assured that it'll still be a tremendous creative effort on your end replicating your reference onto paper or vector.
Use references so that you're practicing and informing yourself on what you need to do to make it look correct.
That's what'll advance your talents.