I usually recommend to go for the challenge that you think is the most interesting/fun instead of directly easiest. Champions add quite a bit of variety to combat, badder bosses make interesting tweaks to bosses, FIMA forces you into a playstyle where you avoid taking hits as best as you can, pharmacophobia forces you to proactively avoid bad situations by taking away the easy solution to all problems, etc. Choose whatever you like

I’d say you can’t go terribly wrong with choosing a first challenge, even the hardest challenge (pharmacophobia) doesn’t make the game terribly difficult if it’s the only thing you enabled (it was my first challenge even), so don’t worry

Enemies can walk over hidden traps as if they don’t exist for some reason. They will avoid a trap only if it’s revealed to you

Not really. I would hate these traps if they were in sewers, but it’s caves, by this point it’s really unlikely that you have no options to deal with them. They give you one turn before you fall and you can use a consumable, artifact or subclass ability to get out of its range and you’re fine

I know, imo it’s still significatly less valuable than the additional uncurse and most importantly full satiety. If I find a health well on 9chal I’m really happy because that means 2 floors without starving

I will not miss an opportunity to say that pharma is the best challenge

that’s usually kind of a waste. Using wells directly also fully removes hunger and uncurses, so why waterskins?

trickshots let you deal onesided damage even to ranged enemies, you can see how to do trickshots in supernewb’s megaguide: https://drive.google.com/file/d/1j8pa2K4KJMtdNX8TQkIPONBrwdlMwSJE/view?usp=drivesdk . Trickshots will usually you get two-three hits in before any retaliation from the ranged enemy, if your wand/throwie is strong enough that may be enough to neutralize the enemy with no damage taken in return. If it’s not enough then you’ll have to get creative

Don’t bother with melee, FIMA punishes the melee playstyle. In basic melee fights you are forced to trade blows with enemies and with each new chapter enemies hit harder and harder but your armor can’t keep up, you will end up taking too much damage from each encounter and slowly but surely lose. There are ways to make melee work (like bolas kiting, armband, chillkiting, ranged melee + haste/flow, etc) and deal one-sided damage but it’s more practical to just play ranged

Ranged runs inherently don’t have to trade blows, for the most part they will hit enemies from afar and kill them before they can get close and scratch you. I think the two easiest ways to win fima are sniper with upgraded throwables, and wandmonk