Due to Anakins bloodline being strong yes? But how come Leia never had any powers?
Leia has the power. She just never develops it fully. It seems that she never wanted to become a Jedi. But she has it. Don't forget, she heard Luke call to her at the end of The Empire Strikes Back.
Will Mc Ren be able to shoot lightning, use telekinesis and such?
Well, the second teaser shows him Force-choking somebody. It is either the Vicar or Poe Dameron. We can tell this by the stormtroopers and the fire in the background. That's because The First Order kills many villagers and sets fire to their settlement on Jakku.
Also, there is said to be a scene where he interrogates Rey after she is captured. He supposedly tries to use the Force to get into her head and she turns it back at him, frustrating him.
Did you listen to some of his lines from the film? Look at my post on page 12. There are Finn, Kylo and Captain Phasma lines. I must say, I don't really like Kylo's voice. I love Phasma's though.