By default, the ToLiSS expects your simBrief briefing to precisely correspond to the aircraft type (by checking its ICAO code). There is a checkbox on the ISCS to disable that if you like.
The CFM56 engines correspond to a “regular” A321 (ICAO code/identifier A321) whereas the CFM LEAP engines correspond to an A321 neo (ICAO code/identifier A21N).
So, depending of which aircraft you intend to fly in X-Plane (A321 with IAE or CFM56 engines, or A21N with CFM LEAP or Pratt&Whitney engines), you need to plan for the same type in simBrief.
Custom airframes for the various ToLiSS aircraft are available here:
Regards,
Tim