Both bed bugs and the insects that spread the protozoan that causes Chagas disease are insects of the order Hemiptera. Bugs of this order are commonly referred to in Spanish as chinches, so this is a good name for either.
So yes, both bugs are closely related. If you want to differentiate, you can always be specific (or pedantic!) and use their scientific names; Triatominae (or triatomines) for the Chagas disease vector and Cimex for bed bugs.
Entomology (from Greek ἔντομος, entomos, “that which is cut in pieces or engraved/segmented”, hence “insect”; and -λογία, -logia) is the scientific study of insects, a branch of arthropodology, which in turn is a branch of zoology. In the past the term “insect” was more vague, and historically the definition of entomology included the study of terrestrial animals in other arthropod groups or other phyla, such as arachnids, myriapods, earthworms, land snails, and slugs. This wider meaning may still be encountered in informal use.
Like several of the other fields that are categorized within zoology, entomology is a taxon-based category; any form of scientific study in which there is a focus on insect related inquiries is, by definition, entomology. Entomology therefore includes a cross-section of topics as diverse as molecular genetics, behavior, biomechanics, biochemistry, systematics, physiology, developmental biology, ecology, morphology, paleontology, mathematics, anthropology, robotics, agriculture, nutrition, forensic science, and more.
At some 1.3 million described species, insects account for more than two-thirds of all known organisms, date back some 400 million years, and have many kinds of interactions with humans and other forms of life on earth.