Question PSBs are occupying large space after building

Hi,
I'm working on a project where I'm using the 2D Animation package. The PSBs workflow is easier since the character parts are already positioned on the wanted places when rigging it. But turns out that PSBs are very large even after compressing and building.

Is there anyway to make it less big? The project is reaching 1Gb size even tho it's only sprites.
I took a look at the Sprite Atlas Packer but the option to tag the sprites wont show up in the inspector. And yes, it's enabled.

I know that saving them as PNGs would help, but there's a lot of them at this point and I'm afraid that this process gonna need me rigging every single character once again.