File per ECU or not?

I'm a new user and have a question I'm surprised I haven't seen here before.

If you're going to work with multiple ECUs in the same vehicle (engine and transmission in my case), is it better to work with both in the same file, or have a separate file for each? Are there any special considerations (including with use of credits) with doing it one way or the other?

Thanks!

Is it safe to assume your car/truck has a PCM and a TCM?

It's perfectly normal to read both computers at the same time and license them. Some computers will require that the TCM be licensed with more credits. Like the later GM TCM's from like 2017+.

For example a GM truck running a E38/E92 with a T43 TCM those can be read and licensed with normal amount of credits, should be 2 credits. From there I never separate them when I work on the files. HPT allows you to pick which computer you want to write too when that time comes. So say you only changed something on the PCM, you can use the drop down menu and click do not write TCM or vise versa with the PCM.

Does that help at all?