Cumulus - Magic 100 Zip

take the lightest bag you can find and/or afford! You do not need a "warmer" one. Most places will be sufficiently heated. As i said in my first post: if all bad things come together, wear some clothes for sleeping or take a blanket. April can be warm, it can be cold, it can have all kinds of weather. I walked mid May to mid June, but also had some weird weather at times (even some snow in June...). So not exactly your timeframe but not completely different. Also forget about the pyrenees. You'll be there 1 or 2 nights and all accomodation there is sufficiently heated. I use the Cumulus Magic Zip 100 for a sleeping bag. Its a bit pricey however.

For the same comfort rating 12C you can have Cumulus magic 100 zip with 240g weight. It's not that light. https://cumulus.equipment/eu_en/down-sleeping-bag-magic-100-zip.html

Take a look at cumulus bags. They can do custom fill (up or down, “waterproof” different fabrics etc ) and custom sizing for it as well if you wish. Not cheap but personally I think they’re the best down bags on the market.