cycle_network=EuroVelo is even documented 
I would use it not only for the complete EV superrelation but also for EV segments and EV stages too.
Back to other questions of EV tagging at the example of EV17:
name
Current mapping for the superrelation of the EV17 is
name=EuroVelo 17 - Rhone Cycle Route
and that is consistent for the other EV routes too. I wouldn’t dream of changing that.
But what about the name-tag of the segments and stages.
@Pyrog is in favour of not using the name-tag, only a ref-tag
The proposal of @Nadjita is using name=EuroVelo xx
ref
That’s the next one. The documented value is
ref=EV17
A value of this form is needed if we don’t use a name-tag.
@Minh_Nguyen has raised a question in the discussion page to that format.
I propose not to change the format, that is well used.