Phoenix Miner 4.2c have full support AMD drivers up to 19.4.3. On later drivers miner woudn't use optimized and double kernels and may (and will) cause many rejected shares.
We need miner update to use new drivers...
why would you want anything above 18.6.1 for polaris?
wouldn't it be nice to have an option for devfee in ZIL? along with coin switching for the time there's no POW on ZIL...

For full support AMD cards on Windows 10 x64 1903 drivers must be at least 19.5.2.
My AMD cards run fine with 18.5.1 and 18.6.1 on Windows 10 1903.
Old drivers havn't support for Windows 1903 version. 18.5.1 and 18.6.1 is more than year old. They maybe work, but can cause system errors and instability. Options in Radeon Settings may not work. For example, didn't work Crossfire settings...
I like Phoenix miner but didn't like his drivers dependence... Claymore's miner didn't have it. Phoenix faster Claymore's miner about 1% (including some lower fee), but with Claymore's miner I can use latest drivers. So I forced to use Claymore's miner. It's sad but true...