Idk Sentai doesn't seem to catch my interest like Rider does. Can't put a finger on it, I feel like Rider's character structure might be more appealing to me.

Personally, I like both of them about equally. There is always times when I prefer one, but I enjoy both franchises for what they are and both have shows I didn't like and shows I loved to death and that are still very emotional to me.

Do actors get very surprised by script about their character?

Gaku Matsuda says originally his character, Zack aka Knuckle was supposed killed by Kaito but thank his character's popularity, Zack didn't die, Gaku was very surprised by this

Mahiro Takasugi states he didn't know about his character, Micchy's Fate. He cannot get Naomi Takebe who is the head producer of Gaim to tell him about Micchy's fate

Do you think Yu Inaba who play Gou and Rio Uchida who play Kiriko are very surprised that their characters was the children of Tenjuro Banno the mad scientist who creates Roidmudes?

the most shocked they probably were would be about "huh, okay" or "huh, neat"

like, a lot of characters didn't die in Gaim thanks to their popularity, mainly Takatora.

As long as the fate of a character goes as planned, they usually work towards that goal and I don't think Kiriko and Gou being Bannou's children was something that was written in later, but was planned all along.
Hase's actor in Gaim for example, knew what would happen to him because Urobuchi told him.

They are usually surprised when changes are made, things they didn't expect beforehand.

Anyone got a clip of the English-speaking politician guy from Gaim?

No, but that did rather surprise me to see/hear that.

Haven't seen one so far.

Has the Drive/Gaim movie been released and or subtitled yet?

Raws are out, but no subtitles yet.