How replayable-4xish is this game?

[Strider]

The campaigns are not linear. Most battles depend on how you perform and what 'area' you choose to attempt engagements in.
The game can be modded in most any aspect, so that you can make your own single battles or campaigns.

BCT and Weird Worlds are each a completely different type from each other.
Each game has it's own demo, and the demos give you a very good idea of what the full gameplay will be.