Deferred rendering path on a 2D game (with lights)

I'm working on a 2D dungeon crawler game that uses lights (maybe from 5 to 10 in average) on each screen. By default light were not working but I changed my sprite's material to be affecting by the spotlights.

So when I'm using low resolutions everything is fine, FPS are always up to 60, but once I try bigger resolutions on my laptop, FPS drop down to 15-20.

This is the first time I'm working with Unity, and I've been reading lots of other threads and documentation about how the view is rendered (forward vs deferred) and which one is better on each case.

I'm not planning to release the game for any mobile platform, neither using AA or shades. Because of that, it sounds like Deferred rendering is a much better option in this case. According to what I read, adding new lights it shouldn't affect significantly the performance of the game. But after trying for a while, using any of them seem to change the performance at all, the FPS are pretty much identical. And just to be sure it was not falling to the default rendering path (forward) I'm printing Camera.main.actualRenderingPath at the start of each scene. For more information, I also changed to use a perspective camera, as apparently orthographic doesn't work with Deferred.

So any ideas or tips about what's going on? My understanding was that deferred rendering would be much better for this very case, but it's suspiciously exactly the same as forward rendering. Am I missing something?

Thanks in advance.