We gotta stop buying cameras, I have 3 film and 3 digital, but only one pair of hands.
Where cost is an issue, and 645 not an option, the 6x6 Bronicas are hard to beat, but they're hardly modern in the broadest sense of the word and you need to be carefull with perishing light seals on the old ones.
Bladds are probably better, but expensive comparatively.
SQ serise is cheap and theres loads of add-ons in the range, I cant say much about RB except it is a beast of a camera and a damn fine machine.
I have Bronica EC, old as the hills, shot seals and completely manual but she takes some beau images when she feels like it, I wouldn't recommend something of that age though for trouble free reliable shooting.
There are metered prisms that do varying amounts of calculations for you, they clip on top of the body in place of the waist level finder, they all have an eye cup, some you look through the same way you look through an slr view finder, others are chimneys that you look down through, non give you the distance between you face and the camera that a wlfinder does.
They do meter, Apperture priority, that is - you choose the apperture and the camera meters and chooses the shutter speed for correct exposure.
Some do both App and Shut priority and have a mechanical/electrical connection that alters settings for you instead of just giving a meter reading.
Maybe the more up to date ones do everything I'm not sure, but there are un-metered prisms also, so read up what your buying.
I'm not certain what is available for every SQ model or which would be best for you, I'm stuck in the dark ages with Veronica.
I would think the SQAi is the most advanced in the range, besides GS1 which is 6x7 btw.
Bronica SQ serise
Load of stuff about SQ and accessories
waist level finder
metered prism and motorised film advance