If doing under 10 pounds I mix by hand in my meat totes.
When doing 20 pounds or more of ground meat jerky or sausage I use the bucket. The bucket holds 20 pounds no problem, the meat tote can hold 20 pounds but there is no room to really mix, you gotta go slow and easy in the tote at 20 pounds.
As for my mud mixer setup I hold the bucket with my feat. It twists every now and again but I'm a big strong guy so I keep it managed well. I never built a contraption to keep the bucket from spinning or a lid to put the mixer through. The 7 Gal bucket and managing the speed of the mixer keep from making a mess with no issue.
As for your wife's 5gal mixer, you are in heaven. That thing will do the job no problem but again 10 pounds and under might be overkill but if cleaning is easy then it's no issue.
When choosing a mixing tool or method I find that capacity and ease of cleaning, out weight ease of mixing. I got tired of mixing 25 pounds of sausage in 2 batches with my 17 pound mixing hand crank mixer. Then when switching sausage mixes it took 20 minutes to take apart, clean, and reassemble the paddle mixer. Not worth it. Now I just hose off with some dish detergent and a hose in the grass and I'm back at it :)