Guidance: Requires concentration, breaks Hex, awful for warlocks. I messed up. Horrible choice.
Acid Splah: I think cantrips made surface effects in EA initial release but everybody haded the surface mess and found it wildly overpowered, so Larian changed it (and firebolt). In other words,
you are right, which means Acid Splash is mainly interesting for its small AoE and not much else, which is a bit underwhelming.
Shocking Grasp: Great cantrip, but it is not high damage and it is melee. Melee + warlock = not good. I agree that the utility factor here is very neat, which is why I think it would be a good candidate for a pact of the tome warlock.
Thaumaturgy: This is an action with a set duration of 10 turns. It does not require concentration, at least not according to spell description ingame. I don't think I have tried it yet.
Light: Indeed.
Your repentance is accepted sir! ;D
I would make one final point about Shocking Grasp versus Eldritch Blast. Since EB is a ranged attack spell it means that anyone within 5 feet of you threatens you and will give you disadvantage on your ranged attacks against any target, including the one that threatens you.
Being able to switch to Shocking Grasp as a Melee Spell attack means you don't have that Disadvantage on the attack roll. Hex damage will still apply, but obviously you lose your Agonizing Blast +4-5 damage - so yes there is a damage tradeoff going down to 1d8/loss of AB damage, but the reaction removal and giving you the chance to run without having to deal with an Opportunity Attack + not having disadvantage seems well worth it to me.
I would argue that Shocking Grasp is the VERY best Melee spell attack cantrip of all of them. Thorn whip doesn't even compare (which is also a melee spell attack with oddly longer range).
AND, AND if some meaty plate-wearing dingus rolls up to you planning to beat you down while you are wearing your Patented Acme Warlock Pyjamas - you get Advantage on that attack roll - just Slap them right in that metal codpiece with the Shocking Grasp - and while they are on the ground crying about their now roasted nutsack, you can scamper away with a smile.
