How much would I gimp my team in winning if I played poppy in ranked instead of malphite?

You have a no fks given adc bursting assassin over a champ with powerful burst and engage in exchange for defense or simply tanky with strong engage

Idk, I guess its not much change

Not at all if you are a good Poppy player.

I have great success jungling her. (Trailblazer) 29 / 0 / 1 Asp Quints Hybrid Pen Reds Armor Yellows 11 Mreg/18 Blues + Rest as MRes/18

Considering poppy can literally solo an entire team i'd say youre fine

Alot.

Poppy behind sucks ass.

Malphite still helps all the time.