So I am going to get either a journey or a kickside as my first “real” yoyo. (I have a Yomega, but after the second one broke I don’t know if they count as real yoyos. May be it is just me.)
Anyway, I am leaning towards the Journey because it has double o rings and it says it has an adjustable gap, but I am still not 100% sure.
So which is more customizable? Which would I be able to get the most different things for?
Journey gets my vote --> Dual o-ring response.
You can customize either one.
I guess one mod you could do to the kickside that you can’t do to a journey is to make it a dual o-ring. 
It says the journey has an adjustable gap. How does that work? Do you shim it or can you do it on the fly?
The adjustable gap is achieved by tightening or loosening the yoyo body on the axle. There’s roughly 1/16 inch of adjustment available.
You can adjust it on the fly as long as you don’t loosen it to the point where the string falls between the bearing and the axle. If you want to adjust the gap, I think shims are best because you’re not guessing at a gap width, and the inner track of the bearing makes better contact with both sides of the yoyo, keeping it balanced.
Can’t much account for the Journey but I love my Kickside…just got it in a couple of days ago and the thing plays very well for a plastic! I was very impressed! Both can be modded to do whatever you need…i’m about to do that very thing to mine. But…for the price i dont think you can go wrong with either throw
i prefer journey
Does the journey have a concave bearing? Or is that just me looking at the picture funny?
Is 1/16 a lot? It seems like it would not me much at all.
Of course I do all my fine adjustments around the house with a 16oz ball peen hammer.
No KK - I believe all YYJ yoyos come with a flat bearing. At least all that I am familiar with. If the journey came with a KK it wouldn’t sell for that price.
The gap adjustment on YYJ yoyos that have it is sufficient to make them go from very responsive to unresponsive. The key to unresponsive is really in the bearing. Lube it a lot and it’s responsive. Clean it and lube it a little and it’s unresponsive.