Great setup. I built mine very similar except I went for the HBA back in 2019. I didn't want the motherboard controller to drive the reads/writes and sometimes the drivers don't work out of the box and you need to side load drivers for installation (from what I read) so I offloaded it to HBA which is on UnRaid support list.

This what I got. https://www.amazon.com/StorageTekPro-9211-8i-FreeNAS-unRAID-6Gbps/dp/B07JZ6FYVC

I then bought a 4x1 SATA cable that plugs into single port on the dual port HBA.

https://www.amazon.com/gp/product/B013G4EMH8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I was concerned about performance, especially when I run virtual machines along with the docker containers while having 9+ people streaming from my PMS at a time.

I actually bought spares of the card and cable, along with an additional hard drive as warranty replacements can take a few days from Seagate (great choice on drives btw). I haven't had any issues (knock on wood desk) other than hard drives going bad which just happens sometimes. Good news is Seagates warranty is fantastic.

Mini SAS to 4x SATA cable SFF 8087 to SATA