Alright so first off, in any situation when you're the player forced into choosing between getting the cs or trading back with the enemy trying to harass, ask yourself this:
"Is the damage I'm going to deal to the eneny champion meaningful ? "
This refers to alot of factors. If you have any type of advantage over them (ex: you can outrade them, you have superior sustain over them), then you probably want to trade back. If there is no advantage or the enemy surrounded by a huge minion wave (minion aggro deals alot of dmg), taking the cs is better. Also keep in mind that there will be situations where the enemy is much stronger than you are. If you are forced into this situation where u know the enemy is going to attack you if you walk up to cs, you may have to miss out on the cs in order to avoid taking further dmg.
For laning phase, you want to be able to stay in lane as long as possible so you don't miss out on the exp from the creep wave. This is especially true if the enemy laner is still in lane. Getting poked out of lane and forced to recall early will lead to level advantages in favor of the enemy. At higher elos, this means they will abuse this advantage to deny you both cs and exp in the laning phase.
Now, if you want to reduce the amount of occurrences for this situation, try to maintain a bigger minion wave (1-2 extra creeps) than the enemy . Doing this means the enemy has to spend more autoattacks on the mnion wave, giving you more opportunities to get free harass on them. This also benefits you in the sense that you also a slight advantage in trades because of minion aggro and you have more opportunities for level advantages.
Now in terms of the meta for adcs, you can pick almost any adc and carry with it. What really matters how good are you on that champion. Some adcs that are pretty dominant in the early-mid game are miss fortune and kallista. Jinx has a very strong scaling and is arguably one of the safest picks due to that. Tristana has good late game scaling and insane turret killing power. Lucian and corki have great burst dmg as ADC casters. Ashe and sivir provide good utility for their team from their ults. ADCs i personally dont recommend unless you're really good at them are vayne, twitch, urgot, and quinn.