Yes, these are Large Milkweed Bugs (the adult and large nymph photos), but the others (the smaller red insects on the Heliopsis) are aphids. The milkweed bugs do not cause any serious damage to the milkweed and do not need control. At worst, if populations are heavy or damaging seeds you wish to collect, you can remove them by hand or with targeted treatments of insecticidal soap.

The aphids similarly cause no serious harm to the sunflower and do not need control, especially this late in the growing season. They may belong to the genus Uroleucon, which prefers aster-family plants, but we do not have an exact ID for them as many in this group look alike.

Insects that feed on milkweed aren't known to cause interference for monarchs trying to use them as a food source. They tend to cohabitate just fine and can be left alone. This study is a bit technical, but you may find it interesting; it demonstrates that the location within a planting where milkweeds are placed can influence how readily egg-laying monarchs find/use them: https://www.frontiersin.org/articles/10.3389/fevo.2019.00474/full

Miri