I'm trying to setup a multiscreen pixel perfect project.
To do this I'll use multiple atlas that is swapped on necessary resolutions. For this there's a lot of examples and scripts.
My question is how should I setup the different resolutions, calculating sprite sizes. Any best practices?
I create all graphics for iPad retina 1536 x 2048 (iPad@2x).
Then I need to create the same graphic for different resolutions.
example Splash Logo
iPad@2x: 500x500
iPad: 250x250 (50%)
iPhone: 115x115 (23%)
iPhone@2x: 235x235 (47%)
But on top of this there's more resolutions (we are still only speaking iOS here, not android).
The image is my setup for different iOS resolutions mapped to atlases (using 4 atlases for 1 game)

The issue here is for all the default values the sprite size is good, but the other screens I use with same atlas (example iPhone@2x the second device resolution). This will change the size of the sprite.
Need some guidance here. Must I have a new atlas for each resolution or is there a fix?
Can I setup pixel perfect for some devices and the rest is scaled to match sprite sizes?