Sorry, still don’t understand point 2. Sure LineageOS with microG comes without gapps and without e-apps.
But anyway, if you want use eOS pie you may have a look here Test Pie Builds for the Redmis 3S 'land'
And when Redmi 3s was coming with Android9 Pie it should be a treble supported device where you can also use the eOS pie-GSI
Have a look here [HOWTO] install eOS GSI on a Treble device