Finding myself needing to fly KLM metal for the first time, this is on 006 ticket stock. With the current flight schedules out of my home airport I imagine I may face this again soon as I prefer to leave in the afternoon eastbound and there are no DL metal options existing these days.

Is KLM C+ middle seat preferable to a regular preferred aisle seat? This is on a 777 ATL-AMS and for travel in 2 weeks there are no longer any C+ aisle/windows available. I reserved 16C for now which is a regular main cabin aisle.

Are there any worthwhile business class upgrade options using SkyMiles on KLM metal and 006 ticket stock? If so, what would it cost me and how do I secure it? I'm on an L fare for this trip.