Everyone was so helpful, I thought I would update this.
My 27 hex is now "compete". I ended up returning the aggressive guppies and now have 3 peppered cory, 7 neons (not sure where the 5 I listed before came from, I got them all at once), and 6 platy (plus one fry that has survived so far.) The platy are two blue Mickey Mouse, 1 sunset, 1 sunset tuxedo and two red wags. I love how active and colorful the tank is and everyone is doing great! I'm sure I'll have an occasional surviving fry and fear that they may have to become food for my angels in the other tank, as I only have so much room.
My betta now has his own 5 gallon tank. Sigh. I wasn't planning on any more tanks, but my SO didn't want me to return him and it's way too cold in this house in the winter for just a bowl. Even if that was desirable. I was contemplating putting some cherry red shrimp in there with him. Might that work?
My 60g is coming along. I had some early losses due to shipping issues mostly, I think. But, because I was ordering, I also probably tried to up the bioload much too quickly in there. I currently have 3 angels, 7 Harlequin Rasbora and two rather lonely rummynosed tetra. Thankfully, I have now found a good LFS, though it is an hour and a half away. They have 2 local breeders of angels as suppliers, so I'll definitely be getting the rest of my angels there once I'm sure my tank is ready for more fish. I'll also be eventually adding more tetra (wondering if the rummynose would school with cardinals? I need some more color in that tank. They try to with the hyper Rasbora occasionally, which is rather entertaining). Then I do still want 6 or so cory (still undecided on type/color) and eventually a gold nugget or peppermint bristlenose.
Thanks again for everyone's help!