The first ten days of the Le Puy, from Le Puy to Conques, are the most stunning scenery on the Le Puy route, making Le Puy definitely the place to begin. You're from Ireland - it won't be that much colder on the Aubrac in late April. I'm sure you have the necessary long underwear and windproofs to make this comfortable.
The Le Puy route is definitely different from the Frances: one-tenth the number of walkers, a corresponding reduction in the available accommodation, most of the walkers speak French, the towns are quite small with no services in-between (for the most part), and higher prices (EUR 35-40/day pp). And, since the French reserve at least a day in advance (months, in the case of groups), you'll want to be phoning ahead for a reserved bed. You'll want to book demi-pension wherever it is available. This topic has been covered in additional threads here in this forum, so doing a search would be useful.