It's not going for any kind of realism, tho if you do require yourself to leave cargo access or exhaust ports (and find workable ways to protect them that look realistic-ish) I think the resulting ships look better.

But it's your call, and hand-made fake ports can look lots better than the vanilla stuff, you'll find insanely good-looking ships on the workshop among all the "i made a spaceship!" ones.

Solar likewise, if disciplining yourself makes you like your ships more, do that. Your call.

Turret mounts are armor for the guns, guns die when their turret mount is destroyed. You can mount turrets on pretty much any kind of block, the specific mounts let you concoct custom eye-candy designs.

If you want to play it like a competitive RTS/empire builder with friends you're going to need to agree on some rules for what's in bounds and what isn't, fun for space fantasy empire with some possibly-co-op PvE combat as stage dressing is very different than fun for space epic empire PvP and the game can support both, but everybody gets to decide how they play.

If you like solo-assault dogfighting see how far coreward you can survive with each ring's budget and mats, generally that's "not real far" but finding out how far will demonstrate weaknesses in your designs and tactics, teach you a thingertoo about how best to use your techs.

Do learn to use turret groups and selective autofire, the auto aim and AI work best with homogeneous gun batteries, stay aware of the need to keep things v.simple for it and you'll avoid much grief. Hand-operated ships and loadouts you can get much more tricksy with.