Description of --gpu-accel and --gpu-loops?
oclHashcat newbie.

I'm looking for a technical description of what those parameters do. So far all I have found is to essentially muck with them and find something that takes you to a happy place. I must have missed something but I've search documents and Googled for over an hour.

You are essentially right. Different cards tune to different settings. Defaults have been selected to give good performance with minimal desktop usage loss. Different algo's also behave differently with these settings, so there is no 1 size fits all.

Technical wise:

--gpu-accel=NUM or –n : gpu-accel defines the workload tuning. The higher this value is set, the harder your cards will work. Higher values can be more efficient on brute force attempts while lower values tend to be better for wordlist attacks. This has to do with the way that oclHashcat stores and retrieves data from the cards GDDR. Be mindful of your power draw, the higher the number, the more power required. There is no set best value. Try different values to find what’s right for you.

--gpu-loops=NUM : This is used for further workload tuning. More specifically, the number of words per unit of work. Essentially provides more work to the left mask.
I can't seem to get more than 75% GPU utilization.

I have a AMD Radeon HD 6670.

The older version of hashcat used to run at 99% and did about 22-23k H/s (WPA). Now I get 72% and 18-19k H/s.

What were the gpu accel and loop settings for older versions? Sorry I'm not sure which older version I used. I still would be using it if it didn't complain about it being a old version and having to download the new one.