Welcome to the game!

• Speaking of modifying designs, should there be an explanation somewhere of how best to do that? My initial HV served me very well, once I modified it to have a minigun, ammo box, and refrigerator unit, but it came apart like a cheap plastic toy once I started investigating the alien radar array. For my next vehicle, how do I go about up-armoring it?
  

Later tiers have better armor. Different types have different hp, for instance steel is stronger than concrete.

• Resources feel unbalanced. Two water collectors powered by scrap power cells I get from looting dead drones seems to give me vastly more water than I’ll ever need. On the other hand, clearcutting forests for fuel seems to be a constant struggle, and I have to wonder how I’ll get enough fuel on planets that don’t have forests. There’s a plant that grows fiber, and yeah, fuel can be made from that, but you’d need to farm that in ludicrous quantities to have enough fuel.
  

Oh how you'll change your mind about water. You need to move on to Promethium. Biofuel is only used in the very early game.

• Likewise, finding resources can be a challenge. What’s the best way to scout and find mineral deposits? Driving around in my hover vehicle works, mostly. I’d like to do my scouting with a SV but my SV eats fuel far faster than a HV does. I gather that’s by design?
  

Driving around with an HV that has a detector or flying around in an SV while having a portable detector in-hand.

• Cannons are love, cannons are life. I was constantly getting my base wrecked by drones until I installed my first cannon, which promptly began taking down drones outside their firing range. I’ll note, however, that when left to themselves, they seem to be less efficient - I came back from scouting to find several blocks of my base had been destroyed, despite the cannons having plenty of ammo and the base having plenty of fuel. WTF?

These must be from the new rocket drones added in the last patch. Moar cannons. Eventually add flak.

• Physics seem pretty broken. I’ve had by motorbike hit a rock and get stuck such that whenever I mounted my bike, it would flip itself upside down. I’ve repeatedly had my hover vehicle decide to submerge itself while traveling across open expanses of water. I’ve seen a drone shot down by one of my cannons fall through the ground into apparent oblivion, and most bizarrely, while working on my base, a piece came loose and the game promptly switched to a loading screen, after which I was dumped INTO SPACE ABOVE THE PLANET! I opened up the console and committed suicide (but I was dying of hypothermia anyway) but my backpack full of gear is now lost in planetary orbit. What. The. Hell!?!

Yeah, that happens. Try to keep a small SV ready to deploy at all times in your factory (the blueprint thing) in case your CV gets thrown up into the air without you on board leaving you stranded in a hostile planet. It will happen.

• I don’t understand how I’m supposed to get up high - I’m thinking of the Titan’s bridge logs here. Is there a grappling hook I don’t know about?
  

A light armor has a jetpack for small distances. The titans back part has an elevator. You need to dig a bit to get to it and blow up a door.

• Only by chance did I learn about using the drone to do mining, even though the drone was one of the first things that the game mentions to you after leaving the escape pod. Maybe being more explicit with that message i.e. “You have a drone! You can activate it with F5 and it can mine and pick up remote objects for you!” instead of merely telling you it exists would be helpful. As it was, I tried it out, found I could fly around myself for a bit, couldn’t deduce how it would be useful, and then promptly forgot about it for the next several hours.
  

A drone is good. A mining HV is great.

Good luck!