I run a Deltec SCA 1351 (equivalent odf the 600ix) and it is extremely simple to dial in. I currently have it tuned to skim very dry dark sludge For skimmate.
Another great option would be the IceCap K2-120. It has been discontinued in favor of the newer “cheaper” IceCap K1 series Which now uses a lesser quality Chinese made pump. The K2s use a better Italian made Sicce needlewheel pump (which is readily available) and has thick acrylic conctructionand titanium screws. They are now deeply discounted at Premium Aquatics.
IceCap K2-120 Protein Skimmer Footprint: 5.1″ x 7″ | Reaction Chamber: 4″ | Height: 17″ Skimmer Pump: Sicce PSK-200...
premiumaquatics.com
I owned one of these and it performed great. Though I replaced it with my current 5” body diameter Deltec skimmer as I felt at 4” in body diameter, the K2-120 was a tad bit undersized for my 57 gallon. It would be perfect for your Reefer 170 IMO.
I use RO skimmers on my 170, 260 and my 425. Each one I have to raise up and inch or so to get the proper height. I cut down a grated plastic container to raise them. That way I have flow underneath the stand.
Though I’ve never owned.a Reef Octopis skimmer, they do have a very good reputation for quality and value and they also have quite a large loyal user base.
I also have the Red Sea Reefer 170, and have been successfully been using the Bubble Magus Curve 5 which is reasonable in price point. Although my aquarium only has two fish, but more heavy on corals. This skimmer has worked well for me.