Do crew members actually give you bonuses? I hired several officers and marines, but it doesn't say they give me any bonuses on the ship screen,. Kind of frustrating considering how expensive they are,

I guess that you get the bonus from the crew, increasing your speed and strength accordingly. This does not show anywhere, but you know how many of each you have. Still, just guessing here from the crew descriptions.

Then there is an aditional bonus when you keep your crew in different proportions. I have read about two, but there might be more:

All marines: 'Marines can't fly': -10%

Crew and officers in a proportion of about 1:1 and being together about 4/5 (or more?) of the total crew: 'Bright minds': +10%

I write from memory. You can check these. I find Bright Minds useful.

My 20 men crew with 10 Crewmen and 10 Officers give me the "Sharp minds" effect :

+ 10% Damage
+ 10% Hit
+ 25% Traval speed

You can see "Crew memver effects" on the bottom right of your "Ship status" screen.

There are two kinds of bonus effects.

1. A bonus for special crew combinations like what Hadral posted. Those effects can be seen on the ship screen

2. The bonus Officers give to crew (combat) performance. This can not be seen on game, but from my subjective experience I do have a lot less losses when boarding with 10 Officers than with 0.

Also, officers seem to survive longer than normal crewman so I even stopped to hire normal crew and instead just have officers and marines.

I have runned a few tests, and here are the results:

To have the "sharp mind" bonus working (+10% dmg, +10% to hit, +25% speed), your overall crew must be composed of 40% crewmen and 40% officers. The remaining 20% can be filled by any type of crew (wether it be pirates, marines, droids or additional crewmen /officers).

As for the "Marine can't fly" bonus - or malus - ( -10% everything), your overall crew must be composed of at least 70% (or more) marines.

(Now why would anyone want the "marine can't fly" bonus on? Well, consider the difficulty of capturing a battleship with only a cruiser, and you actually might want to have that on for such an endeavour.)

As for the officers boarding bonus, the game's manual state that each officer gives a 5% boarding combat bonus, capped at 50% (so 10 officers will do the trick).

The manual also states that there are 4 possible crew bonus on, depending on the crew combinaison, without anymore info. I have yet to find another one; so if anybody finds a new one, feel free to share!

Note that your ship doesn't need to be entirely filled with crew for the bonus to take effect; I was running these tests with a Gettysburg battleship with boarding party cargo, which enable a maximum crew of 150, and kept the total crew at 100 for the sake of an easier percentage calculation.