QNAP / Synology / Others?

Hi, I currently have a QNAP TS412, (probably 10/ 15 years old, all I know is I bought it brand new a long time ago..!), with 2 x Ironwolf 6tb HDD's, (relatively new), and it is working fine, however, it is showing its age with the apps that are available. I am considering upgrading to a new NAS and I have a couple of questions and would like to take your advice please? I have view your great Youtube videos and they are extremely helpful, however, I am having difficulties committing to one specific NAS, I am wavering between a QNAP TS453D or a Synology 920+, then I have just viewed a video on TrueNAS..!!Aarrggh Help, please?
My first question being, are my HDD's, (that are in a RAID configuration in my QNAP where they are mirrored, not too sure which RAID it is?), swappable between QNAP and Synology?
2nd question, I wish to use the NAS for storing family photos, (I would say over 10k and ever increasing), family videos, (current most are 1080p, however, I do have a few 4k and going forward they will all be recorded in 4k), films, (again most are 1080p, however, I do have a few 4k and going forward most will be 4k, PLEX compatible?), and the new NAS will have to be good enough to send 4k, (wifi preferably if possible), to our new smart TV, also, be able for other family members at different locations to view these photos, videos and films.
I like the idea of being able to edit our family videos on a NAS, however, this is not imperative.
The face recognition, to help aid and assist in cataloguing / tagging would be a great benefit to me also.
£600 is towards the top end of my budget, however, a little more I could probably manage to find, if for example a upgrade to RAM would be greatly beneficial.
Which NAS device do you believe would suit my needs best?
Please, please help me..? Thank you in advance. Stay safe and take care, Darren

Yes, it sounds like you would benefit from models such as DS920+ or TS-453D. Something like truenas requires too much attention and maintenance. It is better to stick with leading NAS brands where they add support, bug fixes, and new functionality every month.If your new TV is 4K compatible then transcoding is not required. But if you do have some mobile devices or older TV, using a built-in Video app instead of Plex will allow even 4K conversion on the fly.Moving a RAID from one brand to another is not that easy. The same brand is often as easy as sliding those drives into a new case. But otherwise, you will need to rebuild a RAID and copy data over.Regards to the photos, Synology and Qnap have similar apps, but Synology has more invocations going on on their software side. They also are releasing their new Photos app which is tempting.I hope this helps.