4) Boarding question. How many enemy ship crewmen would a marine company be able to take out? I can see it depending on the ground strength research of each empire, but if both tech levels were the same?

Five carriers just warped into sol from the third system I explored 21 years into the game. Didn't launch missiles, rammed my jump scout to death after I evacuated it back to earth (as in, they came to earth looking neutral, get to earth, ram my jumpship to death and then launch fighters.)
Fighters are all 9999km/s 1 Meson gunners.

Intelligence screen shows them with the swarm picture and they're austrailian-themed. Did not detect any large colonies in the target system.

So, NPR-- Precursor or Swarm?

There are no longer missiles, drones and buoys. There are simply missiles. The flexibility in the new missile design process will allow you to cover the abilities of all three previous missile categories. The drone engine tech progression has been removed.

Missile sensors must be powered. The power requirement for any sensor is equal to its 20% of the sensor strength. So one missile size point (MSP = 1/20th of a HS) allocated to an EM Sensor using a base EM sensor strength of 8 would result in an EM sensor strength of 0.4 (8/20). This would require a reactor with a power output of 0.08 (0.4/5). The reactor space is allocated automatically but displayed as if it was added by the player. Ship-based sensors do not require reactors as their needs can be met from the general power generation of the ship. On a per HS basis, passive sensors are much less powerful than active sensors at the same tech level, which means missiles will require less reactor space per MSP of passive sensors compared to active sensors.

There is no longer a separate 'buoy' category but you can create the same effect by designing a missile with sensors and no engine. The necessary reactor space will be added automatically. Missile reactors have unlimited endurance so there will no longer be a need to replace buoys every few years. While unlimited endurance is unrealistic, modern naval reactors have a service life measured in decades so this is a compromise between realism and a desire to reduce micromanagement. I may add some form of failure during very long term deployment - a failing IFF system on a mine could be entertaining - but I haven't decided yet.

You can create a single stage missile with both an engine and a reactor, which means you can create a self-deploying 'buoy' without the need for a two stage missile, although there are situations in which you might still use a two-stage missile anyway.

...

Missiles that have sensors will now remain on the map forever, with two exceptions:

a) If a missile has geo sensors and no other type of sensor, it will self-destruct when the geosurvey of its target planet is completed.
b) If a missile has a warhead, it will self-destruct when its fuel runs out.