Kind of off the topic- since the topic of the post is the broken installer not even seeing older drivers and installing over older drivers rather than removing them first.
However.
I am not just updating drivers for no reason.
There were lots of improvements / changes in Adrenalin 2019 (https://www.amd.com/en/support/kb/release-notes/rn-rad-win-18-12-2 ) versus Adrenalin Driver, (18.8.2 as shown above https://www.amd.com/en/support/kb/release-notes/rn-rad-win-18-8-2 ) . There is a list of new features in those release notes related to Radeon Overlay, Radeon Performance Overlay and ReLive. Many of the features do work on R9 390X and R9 Fury/ FuryX/ Nano. I have tested them.
You are correct that some features do not work at all.
Auto Overclocking does not work on those cards, but it doesn't work on my RX Vega 64 or 56 cards either. It causes black screening / system hang / BSODs and should be removed from every AMD GPU until it is fixed.
This one:
"Radeon Chill
Improved Radeon Chill efficiency allows increased power savings."
... works sometimes on some games / game API on R9 390x and R9 Fury/FuryX/ Nano and Vega 56/64. - it locks rapid mouse movement based FPS to Chill_Min to save excessive power consumption.
It, along with Radeon Chill in general still needs much more work on all GCN cards up to Vega 64.
It is a missed opportunity for AMD. I would like to be able to have Chill on by default.
I understand that AMD drivers have prevented HBM overclocking since just before Vega launch and I have not seen anything stating any performance improvements to R9 Fury/Nano/FuryX or R9 390X in driver releases for a long time. Indeed, RX580 4GB is showing performance close to and RX580 8GB better than R9 Fury X/Fury/Nano in some DX12 games and it is not because of lack of memory capacity. It might be lack of effort on the Drivers for the older cards, or it may be down to some other reason.
Thanks.