>>724609684
On the one hand, BR2 is a direct sequel with some returning characters. On the other hand, the protagonist of BR2 is a new character that has no knowledge of prior events, and everything the player really needs to know gets explained when it's relevant. I think it's fine to start with BR2 if you want.

Personally, I'm actually more fond of the first game, as it's more unique and ambitious and has higher highs than BR2. BR1 does have more serious flaws, though, and BR2 is a more well-roubded game that's easier to recommend.

>>724609720
You don't have to complete every sidequest and build every facility. Even then, it's not too gindy unless you start trying to upgrade things, which is complete overkill anyway unless you're playing on one of the two unlockable difficulties.