...and here's what they look like today after a week. I'm afraid the tomatoes are going to get unruly... should I be actively pruning or is it too soon..?

You can start pruning to direct growth now, but if you wait a bit, it won't be too horribly late either.

You'll want to cover the dark containers with something that reflects heat, rather than absorbs heat as black does. Otherwise the absorbed heat will cook the plants' roots. Some people use white garbage bags or silver space blankets; I haven't ever done that, but have read that the garbage bags, at least, will disintegrate due to UV damage.

7 gallons is too small a container for an indeterminate like Cherokee Purple (yes, it can be done: but it's too small -- and you may need to water more than once a day; mulching the top of the pot will help somewhat with the water issue).

Also, you will need some major-league -- and much taller -- support: yes, you can prune suckers, but the plants will still grow to 8-10' in height (maybe longer in your zone). Whatever support you use for a tall and/or heavy (all that fruit weight!) tomato vine needs to be anchored firmly outside the container.

I don't grow peppers, but the small rings you have for the tomatoes are often mentioned as appropriate for peppers. (I use them for dwarf tomato varieties.)

Thanks gardenper and missingtheobvious !

Dangit those are all the things I was worried about haha. I can try and get a larger support for the tomatoes, and wrap the container in something white, but I don't think I'll be able to increase the container size unfortunately. I guess my plan for now is to vigorously prune, wrap containers in something white, keep fertilizing frequently, and check on water daily.

I'll keep this posted as I go, thanks again :)