I have been operating for two days with Teensy 3.6 and 4.0 using Arduino 2.0. It coexists along with Arduino 1.8 with TeensyDuino. I had to restart the computer and reload TeensyDuino to get the Arduino/TeensyDuino to find its libraries (maybe just me).

TyCommander does not work (currently?)

Setup was pretty straight forward. TeensyDuino no longer needs to be run and its libraries are loaded automatically. The libraries arestored in:
C:\Users\xxx\AppData\Local\Arduino15\packages\teen sy\hardware\avr\1.57.1\libraries
Set up a sketch/library folder for your libraries.

You can enable serial monitor or serial plotter which I find very useful.

A BIG issue that you will need to deal with is when you select a Teensy board there are two choices for serial port. For example, Teensy 4.0 COM3
and Teensy 4.0 Com3 Serial. The later is selected for you by default and IT DOES NOT WORK. Select the COM3 option and make sure that the Serial Monitor/Plotter accept just a LF.

I do see a bug in the Serial Plotter with respect to selecting different colors for the plots.

Other than that, it seems to be working and I like it.