If you are unsure about your exact processor, the AIO ZIP contains libraries for all architectures (ARM, x86, etc.) and lets the app choose the best one automatically.
After restarting, go back to Decoder settings. Under "HW+ decoders," you should see all audio tracks (including AC3/DTS) listed as "Supported." Play a problematic video; the status bar should show (not SW). Mx Player Pro Codec Armv8 Neon