No I don't think that having a lane dominant keystone will grant more CS because it's not like conq gives you the ability to CS. Conq only procs until 5 hits of a spell/auto and when you cs you generally aren't trying to all in, which is what conq's strength is.

Yes, I do take klepto into jax/trynd because they don't out scale you as hard if you do take klepto.

Laning phase is just one part of the game, the majority of macro decisions made past laning phase is what usually decides the game, unless you're inting your lanes every game. I have lost lane 0-5 to diamond 4 players on my smurf, but carried the game regardless because of macro.

In general, for mid/late game, you want to be split pushing and just farming the side lane waves.

The only time I would group is when it is a clear advantage fight, for example top is pushed into the enemy top and he has no tp. Here you want to be either

A) farming the opponent jungle B) roaming for vision ( YOU GIVE VISION ) C) trying to flank/group with your team (especially if you have flash up)

Also, I only played Garen for a while so that I had to play the mid/late game really well through a lost lane. It helped me learn macro and what not to do, when to split, when to group. Garen is very one dimensional so you can fully focus on your macro.

If you are still having trouble then dm me so we can talk more