On faders 13 - 24: I can understand adding VCAs and FX Rtns but adding master send levels and FX send levels seems like a waste of real estate to me.
If you come from analogue then rather use 18 - 24 (or so) on every layer for your VCAs and/or subgroup masters. This way you can fit more inputs on the strips on each layer and limit how many layers you use.
Then if you have to add master send levels and FX send levels onto your strips; rather pick a low down layer like E or F and add all sends there together (its nice this way so that you don’t get caught mixing sends with returns etc.
Another unrelated but really helpful layout is to assign your critical inputs to the same strip on every layer {eg. talking mics} - this ensures that you have the most critical inputs on the surface no mater which layer you are on and it requires no thinking to reach for the microphone faders in the vent of feedback etc.
I use the following strip assigns [live mixing for house of worship
Layer A
drum channels (8), bass DI (1), mono tracks (1), acoustic guitar (1), rhythm guitar (1), lead guitar (2), keyboard/mainstage/Sunday Keys (2), PC Media ST (1), Vox (4), matrix send level (3)~
Layer B
SubGroup Master (drum, band, vocal) (3), All FX Rtn VCA (1), click (1), MD mic (1), Talkback (1), FxRtn (4), Talking Mics (2)
Layer C
Any unused IP channels not yet in use (spares)
Layer D
All master send levels
There’s no real right or wrong of course
Hope this helps you