...I have a small bandsaw. They're actually intended for plumbers/pipe fitters, etc...they usually come with metal cutting blades.
If you rent one, take note of the size of the blade that it uses. My local blade sharpening shop has band saw blade stock on large reels, they can fabricate a wood cutting blade for the mini-bandsaw in a few minutes for only a few dollars.
A sawzall can work...but make lots of relief cuts and make sure the blade doesn't flex and wander...
I've also lined up all the timbers to be shaped, then used a circular saw. Draw the profile, set the saw to cut ot the line, then run the saw perpendicular to the length of the beams, cutting/wasting away the unwanted wood. Use a fence to keep the blade the required distance from the ends of the beams.
Adjust blade depth, slide the fence over a quarter-inch or so, and cut again. You may need to make a couple dozen passes, depending on the detail.
You can then easily knock the remainder of the waste off the beams with a hammer/chisel and use a belt sander to gang-sand all beams at once.