For those of you who got 100%: are there enough cogs to find to fill all slots?
Theoretically, maybe, because of that one vendor who sells you cogs at an escalating cost. You will hit $100
long before you ever have enough cash on hand to get anywhere near that. I only bought a few from him and finished the game on 82 cogs in total, not nearly enough for all slots.
If 2017 wasn't the great year that it is, I think this might've been my GOTY. Had a fucking blast with it. Really interesting playing this right after Samus Returns too, like it was a good, safe Metroid, but man does SWD2 have it beat in terms of originality of ideas and mechanics.
Gonna go back and 100% it for sure, is there any danger of me not getting enough resources to upgrade everything?
Resource depletion shouldn't be a problem, as money isn't finite even after all the minerals are gone (including the ones you lose permanently to falling rocks, discards from your inventory, etc.). I was a little under what I needed for my final cash upgrade when I depleted every map of minerals/gems, but enemies respawn, so I just put on the various cogs for boosting my income from them (the bounty for killing them with the pickaxe, the difficulty boost that yields more blood gems) and poked everything I could as I traversed the map for my last few items.
I was really impressed with how balanced the cash flow in the game was relative to your map progression and character level; you could tell these developers cut their teeth on genres like tower defense where tuning the economy is everything. It's a subtle thing that most players won't appreciate nearly enough.
Not to fall into the trap of more Metroid comparisons, but I found that Samus Returns had better combat/encounters while Dig 2 had better movement/traversal, which is a really strange thing to say about a 2D Metroid game if you think about it.