I don't own the convertible but I have checked it out. I think it's too small for an overnight bag. The detachable shoulder strap is very thin. Are you near a boutique? Your best bet is to check it out IRL.
When I do an overnight biz trip and carry light I resort to my Herve Chapelier 913N totes. I have them in several colors.
I have this bag and agree with the others it's not quite big enough for overnight. To me, it's more like a tote. I use it for work occasionally and as a travel purse/tote. Sometimes I use it as an everyday bag with the sides fastened.
I love this bag, but it will not serve your needs as an overnight bag. Sorry. [emoji53]
I use the large Rete as my overnight bag now. I used to use it for work when I traveled a lot. I could cinch it for a city bag look and unclasp the side thingies so the bag could haul my files and lap top. Now that I'm not traveling it's a good overnighter.
I have a large convertible and while I'm sure I could fit all the things you've mentioned in the bag, it would definitely look stuffed. It can fit about the same amount as a large Longchamp, but (to me) the Longchamp looks ok filled to the brim, and the Convertible does not.