SUCCESS! I have spent the last 7 hours trying different combinations of settings to see if I can actually get a Blu Ray burned from a file that was created in OBS for Mac.
I have included screenshots of the settings I used and when I was done massaging it, I was able to bring it into Toast 18 and it actually showed the correct file size and then I was able to burn a working Toast Disc Image and it DID NOT try and re-encode the file.
I recorded it as .mkv as you can see in the settings.. then Using the program MKVtools, I changed the audio to AC3, 448 bit rate and saved it back to disk.
Then I used tsMuxerGUI to convert it from .mkv to .m2ts and saved it back out.
It seems that Toast doesn't like 30fps videos because it's looking for the NTSC default 29.97 fps.
UPDATE: One thing I've noticed is now when I click on edit, the video isn't viewable, but the BluRay burns and plays just fine. When you click on EDIT in Toast Pro 17 it does show the video where you can set in and out marks for the burn. Seems like it's a V18 issue.
Toast 17.4 (5589) Update Kills viewing video in the edit screen! I'm thinking the same thing happened in V18.
I just successfully burned a Dual Layer Blu Ray with 28Gig of data on it.
I hope these settings might give others some insight on how to get Toast 18 to work for them.