As a beginner in the art, I have only limited experience.
Of course, I would love the hear answers to your first question.
An element, I never encountered in any other style of TJQ is the felxibility in foot work, bufa, nothing about rooting, the dantian explosions (also different rotations to what I know from Chen village), shatter the whole body, catapulte one's body forwards or backwards. Rooting in a Yang/Chen (sinking in) sense is even seen as a bad habit, which fixes you on the spot, nearly like fixed step phs.
In my other practices of Yang/Chen, the biggest problem form choreographed material to free sparring has always been the flexibility in footwork. Even Huobu tuishou didn't do the job in training the bridging and entering questions, what seems to have a different approach in Hulei. Still needs to followed up further, will see.
Taiwan Hulei from Wang Jinrang was quite clearly pure Hulei, He style (Zhaobao) inclusions in those southern TW schools are only 1 generation old. Both forms are seperated clearly, though, and I'm not clear if anyone here has the Hulei 2nd street, so it might be an addition to fill a gap?
Zhang Suisheng has a vast curriculum, it may be different from orthodox Chen, not as many forms (he git 11 levels for one form), does different weapons and additional exercises. Full monty? Can't answer that!
Well, as said in another threat, interesting times and a long way to go.