questions about setup -Migrating my NAS to new hardware

[Turbocat777]

So I am currently still just using windows and hosting Plex and Home assistant.
I've been hoping to finally migrate my NAS over to new hardware for awhile but it wasn't running as well on the new hardware using the same setup so I swapped back.

-Current setup:
Dell sff office pc
cpu: i5 4570s
ram: 16gb ddr3
gpu: Quadro p400
hdd: 2 6tb drives (almost full) (no more room to add new drives)

-New hardware setup:
case: JONSBO N1 Mini-ITX NAS case
mobo: Topton N5105 Mini-ITX NAS Motherboard (CW-N5105-NAS)
ram: 32gb ddr4
gpu: Quadro p400
hdd: 2 6tb drives (almost full)

I am hoping that not using windows will fix the issues I was having on the Topton n5105 board with Plex and Intel quicksync

I am also not sure but assuming I will need to upgrade my storage before swapping over and can't just use my current drives with the files they have on them.

I am looking to get a couple refurbished 12tb drives now that I will have the space for them in the new setup.

I am open for other ideas and advice as well.