i was considering blu-rays coz then my hdd won't be always occupied
I was in the same spot back when DVD's were in fashion. External drives were pretty rare and expensive back then so I got a whole bunch of DVD's and it took me about 15-20 days to burn approximately 100 DVD's with my shows onto it. This was....6-7 years ago. Eventually, I realized that discs are quite prone to failure even though I had Sony DVD's. Some episodes simply got corrupted while the rest of the disc was fine.
Then I bought an internal drive with an external casing and started using that, which is also an option for you. HDD's also have long warranty periods. Discs are not rewritable unless you want to double your costs. HDD's are just so much more convenient.
In your case I would suggest that rather than putting everything on discs figure out some part of your collection that you want on discs and justify the cost of a Blu-ray drive which itself costs as much as a 2 TB drive
If you have critical data, I would always recommend on keep it on a hard drive. With exceptions to extreme physical damage, data can more or less be recovered from a hard disk, for a cost. An optical disc with any damage is a lost cause.