I’m a 6-year Octane user that switched to E-Cycles, which is over twice as fast as stock Cycles, and somewhat faster than Octane.
• Octane has a few really neat bells and whistles that I find I practically never need in normal day-to-day work.
• I still have V4 Octane (perpetual license) if I need it. And I occasionally need to re-render old jobs with it.
• Grab yourself the free 1-GPU version of Octane and use it for rendering anything that can’t be done Cycles/E-Cycles. I personally wouldn’t recommend buying Octane until you have used the free version for some time and use it to a point that you are very compelled to buy a license or subscription.
• Octane can not use Blender’s materials (Principled BSDF, etc). All materials need to be converted first. Supposedly Octane has a new converter, that I haven’t tried.