Hi Padmasan,
The Behringer 900 series are based on the Moog's System-55 and if I am not mistaken, since it's a, and I am quoting here Behringer.com website:
Authentic reproduction of the circuitry from the "Modular 55, 35 & 15" Series
You might have it so authentic that you need to work with s-triggers. But I am not too deep into that kind of "old" stuff. There are similar discussions already, please refer here within this forum to:
https://www.modulargrid.net/e/forum/posts/index/8645
https://www.modulargrid.net/e/forum/posts/index/8162
But at those times the Behringer modules weren't there yet. I am not 100% sure but I would be careful with those 900 series. At least check it out in more details (sorry I didn't had the time to 100% check this out yet).
Behringer also has the 100 series modules these are Roland 100m based modules, if I am not mistaken those are okay but better have those double checked too.
So generally, you are right with Eurorack, as long as it is a Eurorack module it should be compatible with the rest of the Eurorack modules unless it's a replica of some (old) sort (and that's here the case), then you better be careful and have this checked out very well.
Best is still to go to your local dealer and test a few of those 900 modules in combination with classic stuff like Doepfer, Intellijel, Erica Synths, etcetera.
Or perhaps one of the more "compatibility experts" can tell with 100% certainly if those 100 & 900 series of Behringer can be used 100% compatibly?
Good luck and kind regards, Garfield.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads