"[Question] Level 34, and still I have some basic/newbie questions... help?"

#PokemonGO: Hey y'all.. I'm a 40-something who missed out on the original Pokemon craze, but enjoy the PoGo game. I don't have a lot of the original knowledge like I hear when I go out, but it's been great to learn so far.So I have a few questions.I'm now using PokieGenie to check the ratings of the pokemon I catch or have kept. I'm now labeling them with the value and the attack/defense rating it gives me, such as "Tyrann87AB".How do I know when I should use a Charged or Fast TM item? How can I know which ones I should be changing and keeping? I have a ton of them I've never used. Is it anything under B? Or how does that work? Should I only care about the first letter for attacking gyms/raids and the second for defending gyms? Or does defense matter for defending during a raid/gym battle? Is "A" defense AND offense possible for every pokemon?Also what threshold is worth keeping vs worth looking for a replacement for the number value? Keep anything 80+? 90+? etc?Thanks y'all. Family has fun playing, so just looking to make it even more fun as I get closer to a full Pokedex and work towards level 40. via /r/pokemongo https://ift.tt/2v0nZFM