Motherboard / CPU selection

Hi all, I'm planning to build my first Unraid server to replace an ancient QNAP NAS that has been acting as my Plex and backup server. I've done a ton of research into enclosures, components etc and I feel that I have a good handle on a lot of the components I'll need, but I am struggling to land on a fit for purpose motherboard and CPU selection. In particular, I am not sure whether my selection will cause bottlenecks around PCIe lanes.

My use cases are:

• Plex server: I have plex pass and I use it to serve a few users in the house. I'll want to be able to support multiple (3+) concurrent transcoding streams - I figure I'll need an intel CPU to get the benefit of quicksync
• Radarr/Sonarr/Lidarr/Mylar/NZBGet: I plan to run them in docker containers or plugins, whatever is easier
• Photo and document backup: Storing all critical documents and photos/home videos locally with a parallel backup to BackBlaze B2. I'll leave my media library without backup as I have keys/phyiscals for everything and can restore over time
• Emulation for older school video games (i.e. early playstation, nintendo 64, SNES etc), using something like Retroarch or Plex Arcade
• Home automation: Running Home Assistant sitting on top of a Fibaro Home Hub
• Random assortment of linux VMs - slowly teaching myself software development so I'd want to be able to spin up and blow up VMs for different projects
• Gaming: If I can make it work, I have a spare 1060 6gb card so I'd like to be able to use it to do some casual-ish gaming on the side through a W10 VM. I will be building a dedicated gaming machine for high end stuff so this is more just for when I am fooling around.

Right now I am planning on buying the following hardware:

• CPU: i5 10400
• Motherboard: MSI MAG B460M Mortar mATX
• RAM: Corsair Vengeance LPX 32gb (2x16) DDR4-2666
• GPU: Gigabyte GTX 1060 6gb mini-ITX (removed from an old rig)
• SSD: 2x WD Black SN750 1TB m.2 NVMe in RAID 1 (I can get these really cheap)
• HDD: 8 x WD Red 12Tb (2 party, 6 array - 2 to begin with, room for 4 more)
• HBA: Supermicro LSI 9300-8i 12Gbps SAS-3 HBA
• Cooler: Noctua NH-L9i
• Fans: 4x Noctua NF-A12x25 PWM
• PSU: Silverstone SX700-LPT 700W Platinum
• Chassis: Silverstone CS381

As I said, the main concern I had was PCIe capacity. The motherboard only has 6 SATA ports (only 5 usable with the second m.2) so I do think I need the HBA to allow the array to expand to 6 drives + 2 parity. I am trying to stick to consumer grade hardware rather than getting into the x299's or server grade hardware for cost reasons.