1. What impact does rank have on ship to ship combat, ie. a lvl 16 and a lvl 19 fighting, they both put all there points into decks cargo and are using the same weapons and defenses - what happens?

2. When a planet is attacked/conquered are the structures still intact?

3. About the combat system itself, after a ship to ship fight the screen shows the winner/loser and under my opponents name is some numbers like +5/-5 is this how much better his stats are than mine? Is determining damage simply a matter of subtracting the targets def from my att?

4. I will be hitting lvl 20 tomorrow, should mentally prepare myself for all of my planets to be attacked or is planatary attacks rare at the early levels?

5. I've completed the mission for the beacon jammer, with my legion bonus that planet has around 130 cloaking, till what level would you assume this will keep the planet fairly safe?

I suggest you get your hands on a flux probe and check if anyone has scanned your best planets ... And keep your ship guarding one of your bests as well.

1 They effect nothing but the XP gained (for now)
2 yes
3 No there are maximums and minumums, only Dan knows the details
4 I honestly have no idea, I passed that phase back when they were only 30 players
5 Nothing will keep it safe but that will stop most newbies from finding it

Yeah, what Coth says.
Here's pretty much the same thing he said, needlessly repeated but with more words.

1. You get a bonus when disabling a higher level ship, based on how much higher. Otherwise there's no difference. (I think there should be a penalty for hitting lower levels but that's another thread.
2. Structures remain, but if I understand correctly you can't use them if you haven't researched them. Higher levels have reported seeing their super expensive high-tech worlds being scrapped and rebuilt with lower level stuff.
3. no fair, that's 2 questions in 1! 2 great questions. Wish I knew the answer.
4. I'm level 57 and have never had a planet attacked, but then I have no terran or exotic planets, either. I also keep defenses up on every world, with a 100% legion bonus so it's possible that nobody thinks it's worth the effort for a hunk of rock thats only "very abundant." But I might just be lucky.
5. Anyone over lvl 20 will have no problem achieving 120 scanning. A lot of people think the current cloak system for planets is useless, the only people you're hiding from are the ones that won't attack you anyway.

1) nothing at all. its all about tech and what they have on their ship that matters. 19 will have an advantage because they will have more space, and possibly more tech.
2) yes, but there is a planet age that gives boosts to production for older planets that resets once invaded/colonized
3)not sure how this works, but i think it shows the minimum attack and def your opponent could possibly have based on damage taken/ given.
4)not really. you might have all unique and new planets. if you have a rare planet guard it. there just may be a few players ready to take it if its on their radar.
5) i have 2 beacon jammers on one planet b4 i knew jamming was crap. right now jamming is not worth the space, but it should be once its fixed.

@3 basically its your oponents attack / defense - your attack / defense. So say Someone has 1300 defense and 600 attack and I have 900 defense and 800 attack the numbers would show -400 +200

I have never seen the numbers go past 35, even when I have had over 1000 attack and 600 defense above them. I believe that to be the maximum and 3 to be the minimum damage that can be done in one attack.

Where is everyone seeing minus numbers? The only minus numbers should be inside the damage bubbles. The "+" after the Attack and Defense on the defending ship just represents that you are only seeing the attack benefit from the modules themselves. The only way to determine the actual total attack and defense figures (which include crew) is to use a probe.