Please can people help me the best way to configure my Storage?

Hi all, 
I hope someone can help, 
I’m about to reinstall windows on my server and think that now may be a perfect time to ask for advice on how best to optimize my setup!
My Current Setup is:
- 2x Intel Xeon E5-2630 v4. Supermicro X10 DRL-i mobo, 32GB non ECC ram, Server 2016 DC
- 9 x WD20EFRX 2TB 5200rpm SATA Drives
- ASR-51645 Adaptec SAS/SATA RAID Controller (16 port)

My Current Data Usage is around 90% movies, 7% Files / zips exes etc, 3% pictures, 

Its main duty is as a PLEX server for my family, and storage for all my media and family photos etc.

So, my questions is:
What is the best way to be storing all this data, is RAID the way or storage spaces or something else I’m not aware of?

Performance is a must too as it often must transcode 4K movies, 

Any advice would be greatly appreciated I’m a noob with storage really...

Thanks! 
Ash