Never played BSG, but my friends and I play Nemesis and Lockdown regularly. Highly repayable and usually plays out like a movie plot. I wouldn’t say the rules are simple, but they are once players understand the rules, gameplay is straightforward. Like you said, as long as one player understands them, you are good to go.

The complex part is that there are many variations. Usually, it’s a coop game, but variations can change that:

• add a 6th player as the aliens or the first player that dies can pick up as the aliens so they aren’t left out.

• the missions as you mentioned can pit people against each other. Whether it’s contradicting missions ‘destroy the ship’ vs ‘send the ship to mars’ or straight ‘player 3 must not survive’. Most missions have a cooperative option. The choice is at the discretion of the player, so it will change each time.

• expansions introduce other variables that could pit players against each other. I believe carnomorph has a variant that causes players to go insane. I haven’t played that, but I’m assuming that would create conflict.

Personally, I like original nemesis over lockdown. I feel it allows players to change strategy for survival, which enables people to build trust only to betray each other more than lockdown does. Lockdown is more challenging due to some of the different mechanics, which I feel contributes to players not changing strategies midway through. I’d recommend original if you want player conflict, but lockdown if you want challenging coop (which original supports as well). Might be biased because we’ve played original more, but that’s my current take.

For your questions:

• objectives/missions mentioned above. Players get 2 at the start and must pick when the first intruder appears. Typically you don’t want others to know your objective if you picked the noncoop objective.

• it is expensive, but I feel it’s worth it. As mentioned, highly repayable. Additionally, the miniatures you get are really good - most games like that are expensive. If you like to paint miniatures, it’s well worth the price.

• original vs lockdown mentioned above.

• not familiar with BSG, but horrified seems like a much more simplified nemesis, so maybe that?

Happy to answer any other questions. It’s a fun experience. It’s also available on Tabletop Simulator if you want to try before you buy.

Edits: formating

Edit: I forgot to mention, Nemesis can take 3-4 hours for setup, breakdown, teaching the first couple times. Depending on the number of people and attention span, 1.5 hours for gameplay, 30-45 minutes for setup and breakdown. Usually, my friends and I have brunch with our families as well when we play, so distractions happen a lot for us.

Edit: two other variants worth mentioning:

• instead of everyone taking an individual mission, they do provide a deck of team objectives. All players are focused on the single team objective. Obviously this is coop only, but these objectives are multi-step and require everyone to participate.

• Given Lockdown is the story after what happens after the original, it supports use of the playable characters and intruders from the original. This would allow for a ‘campaign’ where you allow your players that survived nemesis to see what happens when their ship lands and they are quarantined in Lockdown.