Can I run the addon "Usedom in den 1920ern" directly from Open Rails?

Yes, you can use the addon "Usedom in den 1920ern" by calling it directly from Open Rails. Proceed in Open Rails in "Options -> Content -> Browse..." and select the directory of the addon as an installation profile. If you do not changed it while the install process, the default directory of the addon is:

"C:\p-circle\MSTSAddOns\Usedom_in_den_1920ern\"

Your last start with the addon program "USD-Start" should be a start with Open Rails too, before you start the addon with Open Rails directly. This way the for Open Rails needed files will be copied to the right directories.

Why?
The 4 steam engines of the addon are included as AI versions with own shape files (AI=artificial intelligence -> computer controlled vehicles). The animations of the wheel-rods in this shape files have been slowed by a factor of 10 in the addon. Thus, the error of MSTS is fixed, that wheels of AI steam engines always rotates too fast.
Open Rails correct this error by itself. The results of the two fixes is a new errror. Now the wheels of the AI steam engines are too slow by factor 10.
Depending on the simulator you call with "USD-Start", wether Open Rails or MSTS, the according shape files of the AI engines will be copied to the engines directory. So the wheels are shown with the right rotation speed.
Therefore, you find in the directories of the steam engines an "AI MSTS" and an "AI-OR" folder.

 

Some BIN patch versions may have problems with the corrected rotation speed of AI steam locomotive wheels. In this case, you should choose the option "Correct slow moving AI steam locomotive wheels' in the USD-Start Program:

Can I use "Usedom in den 1920ern" with Open Rails without a MSTS installation?

Yes and no. In principle Open Rails is almost independent of MSTS, but one file is absolutely necessary. It is the "tsection.dat" from the global directory of MSTS. Without this, there is even in Open Rails an error message and the addon can not be started.

If the "tsection.dat" is missed in the directory GLOBAL of a selected installation profile
in Open Rails, one can not open the route with Open Rails.

"Usedom in den 1920ern" writes a tsection.dat if it can not find a version of it on the computer while the installation. However, just only this file! All other essential files of MSTS, which are also important for a complete representation of the simulation, will not being created by Open Rails when the MSTS installation is missed. But this way a "minimum" start of the addon will be possible at least. Essential objects like tracks are however missed:

Only dynamic tracks and square steam are shown.
The switches are part of the addon, they do not come from the GLOBAL directory.

 

Click here to see what MSTS files are essentially needed for the addon

 

Can I optimize Open Rails for "Usedom in den 1920ern"?

Yes, turn off the "Forced red at station stops" option in Open Rails. You can find it under "Options -> Experimental".

Why?
Basically this Open Rails option is a good thing and increases the level of realism. It ensures that departure signals showing red just before the train departs the station.
As long as the departure signal shows red, an AI train can occupy the track beyond the signal. This is especially disturbing in one activity, where an AI train is overtaken the players train and occupy the track the player will go on. The player train then has to wait a long time to get "green" until the AI train is leaving the track.
If you now turn off the "Forced red at station stops" option, this will not happen and Open Rails behaves in the activity as MSTS. This way the AI train will not overtaken the players train, but wait next to it at the station.