Welcome to the forums, Diggs!
My thoughts on your questions:
The game was originally balanced around 80 planets, and even though there are very small galaxies available now, that's still a good size to go with; I wouldn't go any larger than that, and I would avoid anything lower than 40, for sure. Somewhere from 60 to 80 should work out well, though I'd recommend more toward 80, particularly considering the size of your group.
As for ship types, there's not too much harm to be had by avoiding simple, but you'll come across some more unusual or difficult to utilize ships on normal or complex. Normal includes things like cutlasses and vampires, which are melee-based ships that damage enemies by colliding with them. They play a bit different from your typical ship. Normal also has more specialized ships like snipers (which are very weak, but great in large numbers for picking off specific distant targets) and infiltrators (which are immune to force fields and can damage ship engines, slowing or stopping enemy ships). Complex introduces ships with some pretty interesting and unique abilities, such as teleporting ships that can travel large distances almost instantly, etherjet tractors (which trap enemy ships with a tractor beam, allowing them to drag the ships out of the battle), and munitions boosters (which boost the attack of nearby ships). If you go with simple ships, you'll still have fun with the game and the ships it has to offer, and you won't run into the problem of getting stuck with a ship type that you're not experienced enough to utilize well. The selection of simple ships is still rather varied and interesting.
Others' opinions on this would be great, too, particularly if they think I'm spouting lies.
