How to check if there is a certain object on given point?

I'm creating a puzzle game and i have a XY coordinate... I need to check if there is a certain type of gameobject. Which function should I use? Should use as an identifier a Tag or a Layer?

More Info:

A block is falling, before it does again a need to know if there is an empty space below in order to commit the movement... So i have the actual block coordinate and I want to check the Transform.Position.Y - 1 coordinate... if there is another block, movement is cancelled and block stops. If there is an empty space, block should move... Like Tetris...

Thanks

 

if the block has collider2d then raycast or overlap ?
https://docs.unity3d.com/ScriptReference/Physics2D.OverlapPoint.html
https://docs.unity3d.com/ScriptReference/Physics2D.Raycast.html

 

Block has not a collider itself (block is a null object containing more single blocks) but if this is the best way to do it i'll add it. Thanks!

 

You can try with arrays, store position/block/... in it and check then

 

i think that's the way i'll try first, idk if this is the best way because there is a lot more happening and probably the best way will be using colliders... Thanks a lot!