Now I've just started another print today, and I still had Cura freeze a few times in the 10 minutes I used it. So without the OctoPrint plugin it's better, but not complelety resolved. I've now checked the log a couple of times and interestingly after each freeze, I found an entry on autosaving being completed (with no entries in the 20-30 seconds before that). So to me it really seems like it freezes every time it autosaves. Is it possible to disable that feature? There's nothing special with my drive setup, just a normal internal SSD... only 45/512GB free, but that should still be plenty.
For now, I just reinstalled Cura completely. I'll then set it up with the OctoPrint plugin as well and report back.
Update - so now I set everything up again (turns out even though I selected "delete all configuration files", my profiles were still there) and disabled the option you mentioned. It still froze again immediately afterwards. From the log, I found the autosave entry again. 19:49:23 is when it froze, 19:49:48 is when it recovered.
2019-04-09 19:49:23,612 - DEBUG - [MainThread] UM.View.GL.ShaderProgram.load [55]: Loading shader file [C:\Program Files\Ultimaker Cura 4.0\resources\shaders\toolhandle.shader]...
2019-04-09 19:49:48,504 - DEBUG - [MainThread] UM.View.GL.ShaderProgram.load [55]: Loading shader file [C:\Program Files\Ultimaker Cura 4.0\resources\shaders\toolhandle.shader]...
2019-04-09 19:49:48,558 - DEBUG - [MainThread] cura.AutoSave._onTimeout [48]: Autosaving preferences, instances and profiles