Your other thread had reference to "Event track" -- which isn't a track type but this thread doesn't make that error so I'll save you from cut/paste from the manual to go through that.

Instead, I'll start with something hopefully more useful.  

You don't have to organize your tracks in any sort of way.  The name of the game is learning what can be done on individual tracks - what you gain by organizing a track as a unit or breaking things down into individual tracks.  This demands learning something about the keyboard and a bit more about the DAW and what tricks you can apply at the track level vs project level vs MIDI channel level vs. automation (or CC data as opposed to note/velocity data).

However, I'll skip past an exhaustive rundown of all of that mostly because I don't know Logic well and to a lesser degree because learning all of the nuts and bolts of a DAW requires time you put into tackling it in small bites at a time.

So ... Enough exposition.  We start with your MODX and how it can differ from other keyboards in the structure of a "sound".  I like that description because a "sound" to me is a unified set of noises that represents one instrument.  Like upright piano is one sound and rock drums another sound and some synth lead is another sound.  Some call these "patches" and most keyboards relate to different sounds by a single MIDI channel.  That all patches in other keyboards usually fit within a single MIDI channel.  The MODX isn't unique but is in the minority whereby a "sound" can span more than one MIDI channel.  I'm ignoring the mode where MODX can put every Part on a single MIDI channel.  In its default mode, MODX is in multi-channel MIDI mode which means every Part is on a different MIDI channel.  And where MODX is in the minority is that there are single sounds like an acoustic grand piano that takes up 4 Parts (4 MIDI channels).  MODX does this for detail so there can be more velocity layers or more customizations per note range or ... Not going to get all into the architecture but it's important to be cognizant of the fact that many "sounds" consume multiple Parts and thereby utilize multiple MIDI channels. 

Now to DAW land.  You mention possibly splitting everything into separate MIDI channels.  That's a valid choice.  I think most DAWs have a way of grouping channels together or merging them or... making that decision work out.  MIDI tracks can have up to 16 MIDI channels (at least as limited by MIDI 1.0).   So each MIDI track could have 1 through 16 channels and I would instead have each MIDI track group together the MIDI channels (i.e. Parts) that make up that sound.  So the CFX multi-Part piano that takes up 4 Parts I would place on a MIDI track that has 4 MIDI channels.  Typically all of the MIDI tracks for these kind of multi-channel sounds are going to have the same MIDI events for all channels.  That's when you're triggering that sound with piano keys and no arpeggio.  Won't get too far into the weeds describing the rest of the picture.

If your song is small enough, it's possible the whole thing could fit within 16 MIDI channels and utilize just a single Performance of MODX.  What you describe sounds like you have one "sound" or I'll say that's a Performance on the MODX for one portion of your tune and another Performance for another.  And sometimes these will be layered (two Performances simultaneously playing) and sometimes in sequence (not overlapping).

If everything fits in one Performance (which I know it doesn't) then you could send the MIDI track(s) to the MODX and in one pass the entire song can be heard or recorded with audio.

If you can't fit it like that then maybe you never have two layered Performances but you switch from Performance to Performance over time.  There's a slight switching delay but assuming that doesn't impact you then you could hear and record this all in one pass assuming the events (MIDI LSB, MSB, and PC messages) were embedded in the MIDI data to tell MODX to switch to a new Performance at the right time.  There's a chart in the data list that pretty much tells you how to figure out how to program MSB LSB PC to recall a Performance.  There's also an "info" screen that shows the MSB LSB and PC for the current Performance which will help you figure this out.  Press the [EDIT] button then see the info page that's a selection in the far left popup menu.

If you must layer two Performances at the same time then there's no way to record this in one pass unless you had two MODXes.  And there's no reason to run out to buy as many MODXes as you would ever need to layer Performances.  Taking a second pass at the recording is the way to go and record to audio so you can use that audio track as a reference while you work the layered track.  

This is the juggling act.  I'd only leave MIDI land in the rear view mirror when I felt like there was nothing left to edit that would be easier to do with MIDI.