Realtek drivers for the most part are no longer being updated. A tech support forum poster still using 2014 Realtek sound driver. My motherboard MSI Gaming 5 last Realtek was 2017 (Version 6.0.1.8010). When I clean install, I just let Microsoft install compatible not Realtek.
As for Fmodex64.dll, friends are replacing with file from Starcraft2 or WoW, to circumvent freezing due to sound error. Of course they have to renew change each time before starting D3. When I reported such to tech support, he reported that they are still gathering information. Note: I have WIn10Pro 20H2, 19042.662. I turned off hardware acceleration for WIn10, discord, and Edge. System info is i7-4790k (not overclocked), water cooled, MSI Gaming 5, 16gb ram, M.2 SSD, RX 580, DVD, extra case fans. Yes, old processor yet is good enough for 8 year game.