Ludu, it's more or less by pitch/weight and cyclic.
Audio groups are by monitor type:
Group 1. 8 Adam A3X, 4 front and 4 rear "upper"
Group 1A. 4 front A3X only "front"
Group 1B. 4 rear A3X only "rear"
Group 2. 4 Adam A8X in front "middle"
Group 3. 4 KRK RP10, on floor front and rear "lower"
1 SVS PC2000 mixed down from A8X and KRK groups
Default cyclic routing by rank, note,, octaves cycled within each group.
For most 8' and upperwork ranks, I use either group 1 or groups 1A and 1B, which are mapped to the same speakers in the RME UFX mixer. I rarely use the split front/rear groups because even surround sets sound better to me with all the samples spread out in the larger group. But I can test front-rear separation this way.
For heavier 8' and a few bright 16' ranks, group 2.
For most 16' and all 32' ranks, group 3.