Can't say what is the best for them but I have used Shindaiwa oil for a few years now and not had an issue. I like it due to the stabilizer. Some of my chainsaws don't run for a few months at a time.
On mix ratio, I always run what the engine says except when I purchased Opti2 many years ago. I ran Opti2 at 100:1 on my Kawasaki trimmer for 6 years. It still runs first pull EVERY time to this day. I swapped to Shindaiwa because my local mower man would not give me warranty if I used Opti2 at 100:1 on my new Tanaka gear.
I have a Yammy outboard on my boat and it has 100:1 stamped on the cowl. Everyone told me to run it at 50:1 because 100 was way too lean. It used to smoke like a bugger when trolling. It runs so much sweeter at 100. It's a gem of an engine.
