Same as for Motion 4: Emitters and Replicators can have their objects shown as Points, Line, Wireframe, or Image. For both, in the Cell Controls pane for the replicator/emitter cell, third item from the bottom:
Show Objects As: dropdown
If I recall correctly, these are the only objects that can be converted to wireframe representations.
Whatever you select from the Show Objects As menu will be used in the final render.
Thanks, but I want to view the full composition in wireframe mode, video windows, text, and other ojects, so when fine tuning moves, it can run at full speed easily, especially on a laptop. I remember working in this mode on the past version of Motion. It was just a toggle, I'm sure. There's no toggle to that mode in the new Motion? Because it's painfully slow otherwise.
I've been through the apple archives for Motion manuals. Could not find a manual for 1.x, but since 2.0 onward, the options for wireframing have been the same: Emitters and Replicators. 3D scene icons are wireframed (that would be since 3.0).
Your speed issues stem from Motion using floating point all the time now. There's no option to use 8-bit (integer) color.
Turn off Field Rendering (docs say it nearly doubles rendering time and it's not necessary for non-broadcast projects) and Frame Blending.
You can also reduce quality and resolution of the canvas (Render > Draft [or Half or Quarter]), but I haven't noticed very much benefit in speed increase by doing this. You can also use the (Render>) Custom settings and turn everything off or set to lowest quality options. [The benefit of this is that Text quality is also included in the resolution settings.]
Another option is to toggle visibility of layers. Turning off layers you don't immediately need to test an animation will speed things up considerably (depending on the object.)
And lastly: RAM Preview. Set a play range of 2 - 3 seconds worth though, unless you have a huge amount of RAM available. Along with that, shut down all other running apps.