Introduction
EX Raiden is fairly similar to his normal self, with the most notable difference being 2 moves. Jumping Lariat Drop is now added to the mix, giving him a decent anti-air, at the cost of the Raiden Combination Body Blow (the reverse dp rekka). Instead of his Flame Breath super, Raiden gains Crazy Train, a rushing super not dissimilar from Balrog's Crazy Buffalo.
Basic Overview
EX Raiden doesn't actually play too differently from the base version. He unfortunately loses Raiden Combination and Flame Breath, which would combo into each other, but Crazy Train is a decent super which, thanks to some startup invincibility on the lvl 2 & 3 versions, can work as a decent counterattack at close range. With Flame Breath gone, his Jumping Lariat Drop is now his main anti-air, though Poison Spray can also work.