The Manix-2 lightweight is a bigger version of the Native, but with the Benchmade Axis style locking system.
Ehh, the Manix is kind of its own thing, with ergos most similar to a bigger Sage or Chaparral (mid height thumb ramp that splits the difference between the no ramp / hump Native family, and the tall thumb hump / ramp on most other Spydies). The CBBL may unlock similarly to an Axis lock, but it has some significant differences from the Axis lock. The Shaman and the Native Chief are the bigger versions of the Native. Also, just a heads up, buying any knife over $40 to $50 from Amazon puts you at high risk of getting a counterfeit. All that aside, I agree that the Manix 2 is a good mid-sized alternative to the Endela. You (or joneb) can also get the Manix 2 LW in either Maxamet or S110V as standard production if you want to play with a high alloy PM steel.
I am not familiar with Bohler K 390 and what it compares to, If it holds an edge similar to S35vn I be fine with that. Not sure if K 390 is worth $45 more than VG-10 ?
It's a high speed tool steel. It has almost twice as much carbon as s35vn combined with 3x the vanadium, twice the tungsten, and twice the molybdenum to form lots of carbides with that carbon. It also has far less chromium than s35vn, so it's far from stainless. It's a tough, highly wear resistant steel, that doesn't have great corrosion resistance.
As for the Endela / Endura, I'm lukewarm on them. The clip screws thread into the liners and I always get wobbly clips or stripped screws from Spydercos that mount the clip that way, particularly the Japanese made ones. But, lots of people still love Spyderco's Seki City made back locks. I'm just a little unclear on what you want. Do you want to try out a larger knife than your Native 5 with equal or better edge retention to s35vn? Do you want to try out a high speed tool steel blade? Do you want to try a stainless steel with significantly better edge retention than s35vn?