For a drum spinner, a fixed shaft is generally the better option as it aids the structure of the machine better than a rotating shaft.

For materials, I'd look at silver steel. around 20 to 25mm dia should be a good starting point. Titanium is another viable option. I wouldn't recommend aluminium.

Both bearings and bushings are viable options and have been used successfully. Bearings are a little more forgiving if things aren't quite 100% accurate.

Ratios are entirely dependent on what speed you want to achieve.

What tooling do you have available to you?