If the NAS is always making noise then it’s not parking the drives. Check the config - I’m not sure QNap does drive parking by defaut if at all. Fron what I’ve seen, they’re a Business Class solution first, consumer second (I have friends in the SMB space, QNAP has been a common solution for their clients), business doesn’t want drive parking.
I have an ancient Drobo that does parking and uses a large fan (so it can run at lower speeds, meaning quieter) - with 5 drives I don’t hear it over ambient room noise (the fridge is louder).
Give us some numbers on space. My NAS is 8TB that I keep 20% free (It complains with less free space and performance drops), my server has an 8TB data drive, with two 4TB externals attached. I replicate data from the server to each device on a rolling schedule for data redundancy, and also use a cloud backup for the important stuff (less than 1TB).
The point I’m trying to make is maybe you don’t need a RAID NAS right now if your critical data size is below available single-drive capacity, and may be better served by multiple drives and cloud backup. (Also, a NAS is still a single point of failure - RAID isn’t redundant data it’s redundant drives. Even with ZFS it’s still a single data store that can fail, which is why businesses still have backups of their RAID systems).
To paraphrase an old racing saying: quiet costs money son, how silent you want it to be? 🤪
Edit: Some links on QNAP drive spindown
https://www.qnap.com/en/how-to/faq/article/why-cant-my-nas-drives-enter-standby-mode
https://www.youtube.com/watch?v=T7ItW76PyBw
Edit2: Even SSD is like 4-6x the cost of spinning disk per terabyte https://diskprices.com/?locale=us&condition=new%2Cused&capacity=8-8&disk_types=external_ssd%2Cinternal_ssd%2Cm2_ssd%2Cm2_nvme
Meh, you got a spare kidney…