The MODE switch is always available.
In PRESET MODE you can have ALL PRESETS, ALL SNAPSHOTS, any combination of PRESETS, SNAPSHOTS and/or STOMPS 4 each TOP or BOTTOM.
The UP/DOWN switches can be BANKS, PRESETS or SNAPSHOTS.
You can swap the UP/DOWN functions to DOWN/UP but you can't disable them in PRESET MODE.
In STOMP MODE, if you have the full-fat Helix (not LT), then you can set it so that you have 10 STOMPS and no UP/DOWN switches.
Using Command Center you can set switches (in STOMP MODE) to switch SNAPSHOTS, MOMENTARILY switch Snapshots (PRESS/RELEASE), or use one FS to go to any Snapshot from any other Snapshot ("stacking"). Example - FS1 in SS1 goes to SS3, in SS3 FS1 goes to SS8, in SS8 FS1 goes to SS6 etc.
Using the PRESS/HOLD setting you can go to either of two Snapshots from one switch.
You can also switch PRESETS, control external MIDI devices, swap channels on an amp, control a DAW, lots of other stuff.