Hello and welcome to the madness!
I’m sorry, this sounds flippant, but if it can drive three stepper drivers, you can use it. The Rambo 1.3 should be fine. I’m not sure what the differences are. There’s not a good chart on the RepRap site.
As a suggestion, build as basically as you can to start, then add features as you need them. i.e., You have the drivers to run dual endstops, but go ahead and run standard serial steppers to start. The firmware is getting much better, and if you’re making your own wiring harness, the serial connections can be confusing at first, but it’s still simpler than the tangle of stepper motor cables, and endstop connectors… Plus, the closer to “standard” your rig is, the easier it is for more of the inmates here to help you out. If you’ve got a bunch of non-standard things going on, maybe one or two folks could even speak intelligently about any problem you have (not that it would stop the rest of us from adding our two cents).
But I ramble as the coffee kicks in… Welcome again! The differences are likely minor and have more to do with electrical robustness than any true functionality. I didn’t see a 1.3L on the RepRap site, so I’m guessing it’s a clone (which is not inherently bad, it is an open source design, after all). If they did a decent job, and you treat it like a RamBO 1.3, you won’t fry anything more than a fuse if something is truly different. Worst case, post up a link to the technical specs, and I’m sure someone will take up the gauntlet just because (but please, let’s try to work through it together, the more you know about your own machine, the better).