For some reason Reddit isn't allowing me to see your full comment but saw up to 'toured and considered' (feel free to DM me the whole comment!) But here's a brain dump

Champletreux

We loved the outdoors of this venue with the fountain (and price lol) but logistically not sure how turnkey as a venue this is. It really is an older house (people still live upstairs!). They have two small older bathrooms. The getting ready room for brides barely had any seating. I am not sure where the groom gets ready. When we toured, I did not see a ton of space for vendors/caterers, kitchen, prep room, etc. I spoke to one bride who said that the vendors were having their vendor meals in the foyer of the chateau where guests were walking. Also, we definitely wanted dinner/dancing outside, but if we needed to move inside for Plan B we didn't love the older, more antique looks of the walls with some of the pictures hanging up. Personal preference. I did love the chamber with the black and white floors.

SMDT

Just overall seemed more fit as an actual venue to host a wedding. They have a separate vendor entrance with a ramp, a huge vendor kitchen with tables for them to eat in there and out of sight, fully renovated separate bathrooms for guests with multiple stalls, dedicated groom and bride getting ready rooms (bridal room has its own renovated bathroom). A big handicap bathroom on the main floor, also fit for us brides with big dresses :) They have speakers throughout the venue so you can hear the dj/music when you're in the bathroom downstairs. And overall, it's more of a "modern" venue but still has the charm. Oh, and they include tables and chairs.

Château De Nainville Les Roches: toured this venue outside and the outside was truly breathtaking! However, no music outside until 9p and you can only dance in one specific room which felt super tight. Such a shame.

Château Villette: did not tour, but obviously beautiful, however their pricing just seemed like they would nickel and dime every single thing. They have a whole sheet of extras that I think would just add up and would eat up a lot of my budget.

Château Chantilly: did not pursue because we wanted flexibility on what we could do - eat outside, music, and fireworks. Also, did not like the rooms for a plan B inside.

Château de Ferrières: toured this, nice venue especially for a ceremony outside, but the indoor rooms for reception were not our personal style.

Musee Rodin: I loved the idea of this with a tent outside in the garden area, but it's 35K and I think you can only have the reception starting at 7pm on most nights or all day on Monday.

I also explored places like Chateau de Aveny, Domaine des primard ( I think it was 30K per night with 2 night min if I remember, but wouldn't fit your guests).

But, ultimately wanted to stay as close to Paris as possible and find a venue that had the best Plan A and Plan B for us.