If you are looking for vanilla experience on your Samsung Galaxy S9 and S9+, there is no better ROM than the Resurrection Remix, whose developer has churned out many quality ROMs for various Samsung and non-Samsung android devices in the past. This is a ROM for Exynos devices only and bre5 vendor is needed before you install this ROM.
Installation instructions for this ROM:
* Install the S9+ TWRP and make sure it’s fully functional
* Download the build and flash it through TWRP. Download link
* Install the Gapps and addOnSU if you want. This will give you optional root access.
Default density is set to 560 on the S9 and if you think the text is too small, change it to 600/640.
This is a great ROM that is based on cyanogen mod, slim, omni and original remix firmware builds. It is a perfect mix of performance, features and customization. A lot of things have been tweaked by the developer and included in this ROM for the S9 and S9+. Everything works on the official Lineage build is working on this ROM.