Fresh Build - need motherboard and RAID advice

Net/net: I want to build a new headless server to be used as a Plex host as well as general file server/backup server on my home gigabit network.

My goals are: long term reliability, and as low heat in the box as possible. I realize a lot of that has to do with the case and cooling plan but I want to start with low-wattage devices.

My prior build (12.x system that ran for years) was “ok” but I had a hardware RAID controller and 4 7,200RPM drives which combined drove a LOT of heat in the system and I think contributed to eventual hardware failure.

Form factor doesn’t matter; small would be nice but not a deal killer. Questions:

  1. Can I rely on motherboard-based RAID and avoid having to go again to a HW RAID controller card? Will openSUSE 42.x tolerate that?
  2. Any advice on a good motherboard to consider would be appreciated. Intel NIC would be nice. Anything that is reliable and plays nicely with openSUSE.
  3. Something that takes a low-wattage (but good performing) CPU would be great.

thanks!