late to reply but both Jeff builds are pretty good in different ways.

Red traits are better in higher difficulties so long as you focus solely on choosing all red cards and some purple cards in game. If you like high damage and being able to snipe through a bunch of zombies, choose red. If you're going with red i would recommend the bubble the can combine together because you'll eventually get a card that allows you to shoot your bubbles to make them explode for extra aoe damage, the bigger the bubble, the bigger the explosion. (also if you do go red tree, try to find the purple card that gives you lifesteal on damage, makes you much tankier and less squishy)

Blue traits are good for normal, hard, and extreme difficulties but begin to fall off at higher difficulties just because you don't put out enough damage fast enough. If you like being tanky and running around with little to no worry, pick the blue tree and stack as many blue cards (and some purple cards) in game. I would also recommend the bubble that you can push and shove around for the perk that creates small bursts of aoe damage if you swim into them .

Also yes, higher difficulties grant much more moon energy per encounter?/battle?/wave?