Line weights in model
I've noticed that as a default the lines in my Revit model are very thick when I zoom in close, in comparison to the lines on your demonstration videos. For example, in the "Splitting Elements" video where you zoom in to show how the split tool has achieved a 25mm gap between wall portions, when I repeat this exercise the gap is not visible on my program as the lines are too thick & merge together. I see that it's possible to remedy this by clicking on the "Thin Lines" icon, which states that it shows the lines "as they will be printed". I'm unclear what this means or how it works - should we be working in model space with the "Thin Lines" tool activated, or normally not? If not, is it normal that my lines show quite thick when zoomed in close, and merge together? This seems to reduce the ability to work accurately. Thanks, I'm just looking to get some clarity on this and how it is best to work in relation to line weights within the model.
Model Line weights in Revit are handled automoatically by the software. That is, (for example) Walls will be drawn in certain line weights- and this will vary for their elevation, section cuts, etc.
For any given line weight, Revit will actually keep these sizes relevent to each other even when zoom in.
The "Thin Lines" tool is there simply to see EXACTLY what is going on at junctions etc, where "normal" line thicknesses would get in the way. I would suggest that the vast majority of the time you will want to switch "Thin Lines" OFF- that way, you will see on screen EXACTLY the representation that would come out of your printer.
To further complicate this just a little more!!.....
Revit draws lines at different thicknesses (for the same line weight) depending on the VIEW SCALE.
To see this in action for your self- place a piece of wall in your model. Zoom right in so that the end of the wall (in plan) virtually fills the window. Make sure Detail Level (for this view) is set to Medium or Fine- so that you can see the layers in the wall build-up.
NOW: Just play around changing the View Scale (for this active view)- notice how Revit adjusts the line thicknesses at different Scales.
I hope the above goes a long way to answering your question- if you are still not 100% sure / convinced, please come back to us.
And with regards the split-line exercise, I think your line thicknesses look different simply down the View Scale you had chosen in that view.