I don't know if it will helps you but, I had a similar problem.
I resolve it by adding a border to my assets in "TexturePacker".
You just have to open the "Advanced Settings"
And at the bottom, just add a border padding of 2 pixel as it recommended.
It should help you =)
Sure there is!
If you have a grid you do not need a collider. By definition grid works instead of collider.
What you need to do is:
Store (and retrieve) each tile address into (from) data structure (hashtable, dictionary or array, list). So now when you select (or do something) with one tile you can immediately access its neighbors!
For simplicity lets ...
TL;DR: WebGL Demo & UnityPackage Download
In the past I have tackled a similar problem by attaching a node component to each grid object. Each node component in turn keeps track of its neighbor nodes in a what could be described as a recursive manner.
In my experience this approach works with thousands of nodes in a game world in a WebGL ...