It's a 2006 Dell Inspiron E1505 with 2GB RAM, 120GB SSD but just W10 without any hyper cloud, volumouse or such. It's stock and clean. I don't get any audio buffering issue.
I also didn't set the drive or any device to sleep. It's a clean W10 install and it was so weird not having to find any driver.
Your machine is far better than my oldest iron on W10 and so it must be something added after W10. I can't guess which it is.
HOWEVER IF I WAS TO GUESS, I've lost count of Seagates that cause odd delays and issues. I'd try this without the old drives. They can create odd issues as the read or write can cause the OS to pause.