It depends from Country to Country in Germany, Switzerland there is usally a fixed timetable for a the platform this means the train starts every day from the same platform :) 

In Czech Republic or Italy  it works like an Airport you get your platform atleast 15minutes before depature throw Monitors and Boards across the station. On top of that many countries have own Apps that Show from which platform which train departs. Because of that i recommend to use beside the Railplanner of Eurail a local railplanner app :) 

If the planner gives a 7-minute connection, then it can be done in principle. If you let us know which connection that is, we can advise an app or website to know the platforms in advance.

Depends on the Planner. Interrail Rail Planner does not use any minimum change times provided by the national timetables per station. It only uses the same time for each station (that you can set by your own).

I think 7 minute connection is too short, unless it be in a very small station, in a small town.

That would be strange and would be a bug. Any planner should use both. The minimum change times per station are part of the timetable data. Do you have any examples where the Interrail planner ignores the minimum change time of a station?

My example that i had was that i had to change in Paris within 10mins from Gare du Nord to Gare de Lyon SNCF says atleast 30mins DB even 40minutes

Once in Berlin HBF (two parts) standard by german rail is min. 8mins from HBF tief (tunnel) to HBF oben (elevated) Railplanner thougt 2mins are enough. 

Wow, that was a serious bug. Although it seems it has been fixed: Paris Nord to Paris Lyon now shows up as a 40 minute transfer and Berlin Hbf to Berlin Hbf (tief) is now 9 minutes, just like in the DB planner.

You are right. My examples where in Zürich HB, but I cant reproduce them anymore. But I wouldnt see it as bug, more as a feature. I used it several times in past to find  some running shoe connections. But it was definitely something important to know