I know that Rampant has its own toxic and other types of biters same as in these mods. So with these mods I will have two kinds of Armored biters or Rampant will somehow merge them? What about toxic and explosive? Will they also scale according to Rampant biters level? Will they use the improved AI?

Will they also scale according to Rampant biters level - no
Will they use the improved AI - yes

WIll Armored Biters from the mod be merged with Rampant's Armored Biters?

No. The biters from Armored Biters will remain.
Also, Rampant Fixed will use the animation from Armored Biters for three factions (regenerative, armored and juggernauts)