135 Surveillance works for Kamacite but I think you'd be safer at 145 for the Otter. There haven't been any reports of ships with 135 surveillance getting Otters.

As for what's the "point" of the Syldra parts -- the idea is to be able to mix and match to get the kind of ship you want to run. If you look at each of the stats for the various parts you'll notice they all have tradeoffs, where an increase in one stat is paired with a decrease in another. Each of the Syldra parts is best in its class *for what that part does best* but it might have equally high downsides to balance that out. So you're going to want to mix and match parts depending on whether you want a really fast sub or a sub that can hit a lot of sectors in one trip or a sub that gets large stacks of loot that's stackable (crafting mats) or a sub with a really good shot at getting rare items.