With those size pots you want only one tomato plant per pot. Cherries are indeterminate and can grow huge and with an appropriately sized root system.

I really have no experience growing in your climate, but we cannot plant out tomatoes here until late May at the earliest because of cold weather so those plants seem very small to me. Mine, planted just a few weeks ago, are already about 4' tall and flowering heavily.

Yup. Take out all but one tomato plant. If you are careful and move them gently, you can save some, or all of the rest.

The large plants do look like sunflowers. Again, I would be tempted to dig them out very gently with my hands and save everything.

If you don't have anywhere to transplant saved seedlings, you can always cut the extra's at ground level so as not to needlessly disturb the roots of the ones that are staying.

HTH,

Linda

I feel bad throwing out the excess plants but I guess one-plant-per-pot rule is what I'll have to do.

They were all filled with emptied and filled with new soil and compost.

Compost? You probably threw some tomatoes in there, and tomatoes have seeds in them.

If I threw tomatoes into the compost, I guess the heat from it didn't kill the seeds.

Your compost would have to get up to 140F to kill these seeds. The inner part of the pile may have gotten that hot, but unless the pile is diligently stirred, the whole pile won't get hot. They're called "volunteers". If you planted hybrids last year, and they got into the compost, no telling what's popping up this year. So unfortunately, one would like to pluck the volunteers, and leave the sprouts from the seeds you planted, so you know what you have. Looks like it's too late for that now.

That being said, sure, plant 'em out. You got tomatoes. Though you don't know what kind.