So once again, packing lunches is a new thing for us. There's more about what we've packed so far here.
Today I'm talking gear. When I was looking around deciding which lunch gear to get, not all of my questions were answered, so I hope this is helpful to someone!
First up, here's the bag we picked, it's a Wildkin double decker. I really like the idea of having two compartments, one for cold, one for warm. Or one for cold, one for snacks or something.

I bought it on amazon, finding a REALLY good price on this one specific color in the summer.
Reviews reported that it would fit an Easylunchbox in the bottom section. Since my ziploc divided containers are the same size, that was important. These things should be stored flat, not sideways! I was afraid the bag would be huge, but it is a great size.
It seems to work pretty well, I don't think it insulates as well as this other lunchbag we have (pottery barn - discontinued), but it works! It also has a long shoulder strap, which is great as the girl doesn't have a locker, so she has to carry her lunch with her all day.
She brings a water bottle every day that goes in her backpack pocket, so it doesn't need to fit here, but smaller water bottles (not her 24oz camelbak) or juice boxes would totally fit in the upper section with other food.
We are using two main containers. Ziplocs and Lunchbots. The ziplocs are great containers. I'm still trying to use less plastic, but these are just REALLY easy to pack. Reviews say that the lid seals better than the Easylunchbox, but may not last as long. Supposedly they are BPA free.

Here's how a ziploc looks in the lower section of the bag (it does zip):

Here's how the ziploc container (again, about the same size as the Easylunchbox) compares to the lunchbot (duo pictured).

Lunchbots are about the same size as the large section of the ziploc.
But speaking of lunchbots - I love them!

I ordered one (the duo as it seemed the most versatile) on amazon, but then found them on sale at Zulily and ordered two more. Glad I did! Besides packing flexibility, I like having them around to pack for the boys/me if we're heading out. So we have the uno, duo and trio boxes.
They wash up great in the dishwasher, and I do have really hard water, so you'll see some spots, but they come off easily (when I'm not lazy).
The lids go on securely, but aren't leakproof.
If you look below, you'll see why the divider isn't leakproof either.

See how juicy stuff would flow right through that seam? So I say hummus is a yes, but applesauce/yogurt, etc are no-gos.
Lunchbots are more expensive than plastic containers for sure, but they should last forever.
You can totally pack enough food, even for an adult, depending on how you pack them. If we're not packing the lunch tight, or are packing sandwiches or something bulkier, like our piroshki, then sometimes we need to send two of these containers.
Next up on my perfect world wishlist is the bento trio. It's a bigger size lunchbot, close to the ziploc size. Sounds ideal.
Here's how a lunchbot fits inside the wildkin bag (it is sitting on a thin ice pack in this photo).

And lunchbots fit in the top section, too - ziplocs only in the bottom. Yes, we keep a tin of tiny altoids in there, too! Inspired by my always-too-garlicky hummus. ;)

You can almost fit two lunchbots in the bottom section. I'll bet it would zip, but haven't felt the need to cram them in like this.

I got a set of these little dipper boxes from Easylunchbox.

Here's how they fit in the ziploc:

And the lunchbot:

They're kind of a weird size, I think. Great for something like salsa or nuts, a bit big for salad dressings, too small for applesauce or yogurt. In a perfect world I'd have these stainless lunchbot mini containers, and while I believe you get what you pay for... the plastic ones were a lot cheaper to start out with.
Oh, also I haven't had much luck washing the little dippers in the dishwasher - they flip over.
Now for hot lunch: We got the 16oz Thermos container (like this, but our color isn't showing and I definitely didn't pay that much. If you keep an eye on prices you can really get good deals on amazon).

Seems to work fine, the folding spoon is nice. She told me they have a microwave at school, so maybe this wasn't as big a deal as I thought. I do prime it, by filling it with boiling water before I fill it with food.

*Edit: We've now tried her thermos for cold smoothies, too and it works great! She makes her smoothie at night and sticks it (and her empty thermos) in the freezer. In the morning I thaw the smoothie enough to get it out of the container and into the thermos (I think it would be way too hard if we froze it directly in the thermos). By lunchtime it is 'the perfect consistency!' - slushy.
Here is how the thermos fits (top section only) in the lunch bag.

Now you may remember that we already HAD bento containers. Cute, cute bento boxes. Well, years later they really smelled 'plasticky'. Very. I wouldn't want to eat out of them. Then I looked up BPA info and it looked like ours weren't BPA free. So we ditched them. However I did keep some of our bento stuff:

Someday I might want silicone cups but for now I am using what I have, which are these cute daiso ones paper ones. I kept a couple of little forks, they are great because you can put the fork back in the little box, which keeps the lunchbag clean. However they're not very sharp, meaning probably not so effective on salads...
I've already shown you the silicone smoothie pops, which only fit in ziploc or lunchbot uno. They are working well, but reportedly are just 'cold drinks' by the time lunch rolls around. But that's fine.
I also kept a couple bento straps, just for fun.

I already told you about our cloth napkins.
...Let's see... ice packs?
We have the 'standard' ice pack blocks, but also the slim ones, which fit above and under whatever is packed in the bottom section. Those are perfect for this bag/box combo.

The only thing I'm missing is a smallish container for a single snacky thing, like popcorn, one muffin, etc. to be packed separately for a snack. I may pick up (or put on my Christmas wishlist) a couple of lunchskin reusable bags for that. I've only packed two disposable baggies in her lunches so far, but I'd rather not use any.
I still really enjoy packing lunch kinda bento style. The divided containers make it very easy to add variety/nutrition, as we found out years ago. Also it's not a big deal if you run out of bread or anything. There's always little bits of something in the cupboards that will fill the boxes.
I'll leave you with the last couple of days' lunches:

Quesadilla with salsa, hard-boiled egg, orange slices, chocolate chip cookie (broken up to fit!)

Leftovers from last night's dinner: Indonesian pineapple spicy chicken salad. The Uno container has cabbage, carrot, and red bell pepper, the duo has chicken, peanuts, peanut dressing, crushed pineapple (all to add to the salad), and a muffin (leftover from breakfast - for snack).
Yes, I do put the lids on the mini dippers, but they look better in photos without.
I think that's it, hopefully someone can use this excessive information - Any questions?