I switched from Bartender to Trinity a LOOOOONG time ago.

And your question about switching between solo and multiboxed play? Trinity has "templates" that include your keybindings, button layout, and even MACROS. Yes, trinity can swap macros on the fly.

I have a bunch of templates now: raiding, raiding specific encounters that I need specific macros for, multiboxing as enh (for dailies where I don't want to respec), multiboxing as resto. (this is on my enh shaman who switches to resto when I multibox)

The fact that it swaps out my macros is priceless. I have long since run out of space on the standard /macro UI.