Question on new build

So I acquired an older PC from work that I plan to set up as an unRaid server. Here is what the specs are:

Motherboard: Gigabyte Z68A-D3H0-B3
Processor: i7-2600K
Memory: 16gb

My current set up is an old Mac Pro (2006) that I’ve upgraded the processors and memory and video card as much as possible (so it registers as a 2,1) running Plex and Usenet downloader software. I’ve already purchased a HP-290 to replace the plex part. This new server will basically be a NAS and seedbox and possibly a couple VM’s for messing around.

I currently have 4 1tb drives plugged into the motherboard just to experiment with unRaid - and I plan to add at least a 256gb SSD that I have lying around as a cache drive and about 17 more TB from my current backup solution - an old Drobo5N. (currently working on ideas on how to migrate before pulling and formatting them)

I ordered an LSI SAS 9210-8i from eBay as recommended on this forum and I plan to flash it to IT mode. My question is - do all the hard drives connected to the LSI board need to be the same interface? i.e. can I have 4 SATA drives hooked up to one port and 4 SAS drives hooked up to the other - or do both ports need to be the same?

Also, other than more memory and the LSI board, are there any other upgrades i’m not thinking of?