You can cut where you've shown. Process of rooting is same as in doing an 8" piece.

The plant underneath the yellow line will also grow foliage close to the cut line.

I would cut the blue pot plant in the vicinity of where you placed those marks. Perhaps a little lower and try to align cut as much as possible just above multiple leaf nodes. That way you have a good chance of multiple branches forming.

The black pot I would cut lower. While scale is hard to see in the image I would try to stay about 8 inches from the bottom branch looking for the best spot to cut just above as many leaf nodes as possible.

Cutting techniques which are proven to work well for me include the plant being well hydrated in the days before the cut. Using a thin kerf saw or blade instead of bypass shears that can squeeze or crush. Angle cutting on the mature plant to ensure water does not have a place to stand. Use of caulk, wax, or pruning spray to cover the wound after it has dried. If you angle cut then you need to perform a second flat cut on the cutting for best rooting practices. See Citizen Insane's research post about how roots grow from different cuts.

As far as the cut branches. Again scale is hard to read in these images but they don't look to excessively large to me. They might be a bit more unruly and require more bracing/supports to isolate and prevent movement but that should be about it. Generally speaking it will probably be easier too. I would just strip the leaves, let them callus up for a week or 10 days with rooting powder and then throw them in a 1 gallon pot with 1 to 1 soil and perlite. Then put them in a warm spot. Plan that they will be the first ones you up pot to a 3+ gallon container next year.

While you didn't ask about timing. It could be done anytime over the summer but my preference is to prune in the spring before the growing starts. Some cultivars do have die back issues if they are cut late in the season.

Good info, thanks guys.