New NAS to replace current QNAP

[Enquiries]

I have a QNAP TS-251+. 6 yrs old. Original 1T WD Gold drives. 40k plus hours on drives and old QNAP technology.
-backup files, financial data, store movies, pictures, some music (not much), PLEX for home use and to share via internet with my kids. Also have one camera in place, planning for second - store recordings. My use isn't huge, but I want another six to seven years from a new NAS. I have 1 unused WD Gold 1T drive, two with data (mirrored set in the NAS). -two NVME's as new "drives"? or Sata SSDs? or WD Gold server level drives again? Would like to use my current drives until they die - or is that a bad idea? I have looked at Synology - old technology. QNAP - a little better hardware, used to the OS. UGREEN - too new, no PLEX support. Terramaster - still has software growing pains, but seems much better hardware for future proofing, but struggling software. I have built many PC's but no longer desire to spend hours messing with software configs. No self build

[subfam2]

I have a QNAP TS-251+. 6 yrs old.  Original 1T WD Gold drives.  40k plus hours on drives and now rather outdated QNAP technology. 
My gneneral use is:  -backup files, financial data, store movies, pictures, some music (not much), PLEX for home use and to share via internet with my kids.  Also have one camera in place, planning for second - store recordings.  My use isn't huge, but I want another six to seven years from a new NAS.  I have 1 unused WD Gold 1T drive, two with data (mirrored set currently in the NAS). My questions are:  -two NVME's as new drives?  or Sata SSDs?  or WD Gold server level drives again?  Would like to use my current drives until they die - or is that a bad idea? I like the idea of being able to use different sized drives at the same time - but also understand that would cause issues with simple drive mirroring.  Unless I can set up two mirrored systems in the NAS? 

I have looked at Synology - old technology.  QNAP - a little better hardware, I'm used to the OS.  UGREEN - too new, no PLEX support from what I can see.  Terramaster 424 (base, not pro or max) - still has software growing pains, but seems much better hardware for future proofing, but struggling software.  I have built many PC's but no longer desire to spend hours messing with software configs.    

This is my personal inquiry from a few minutes ago on the main webpage of Nas compares - then joined the forum.  I have modified the initial inquiry some so please take a look at it in my post here for the edits.  I appreciate all perspectives!  Thx