A warning about answers to questions like this:
There are serious questions about what major historical characters actually believed. E.g there's serious question whether Nestorius -- one of the arch-heretics in the area of the Incarnation -- actually held heretical opinions.
With your original question, the period during which the Monarchians functioned is not all that well documented. We often know only snippets from what they wrote, and many early writers are known only from quotations by people who were hostile to them. That makes it hard to compare theology from that time with modern theology. For that reason, and because two fairly different theologies are both characterized as monarchian, I'd be reluctant to use that term for modern writers.
To give you a sense, here's a quotation from the early 20th Cent Catholic Encyclopedia:
"The sect probably died out about the middle of the third century, and can never have been numerous. All our knowledge of it goes back to Hippolytus. His "Syntagma" (c. 205) is epitomized in Pseudo-Tertullian (Praescript., lii) and Philastrius, and is developed by Epiphanius (Haer., liv. lv); his "Little Labyrinth" (written 139-5, cited by Eusebius, V, 28) and his "Philosophumena" are still extant. See also his "Contra Noetum" 3, and a fragment "On the Melchisedechians and Theodotians and Athingani", published by Caspari (Tidskr. für der Evangel. Luth. Kirke, Ny Raekke, VIII, 3, p. 307). But the Athingani are a later sect, for which see MEDCHISEDECHIANS. The Monarchianism of Photinus seems to have been akin to that of the Theodotians. All speculations as to the origin of the theories of Theodotus are fanciful. At any rate he is not connected with the Ebionites. The Alogi have sometimes been classed with the Monarchians. Lipsius in his "Quelenkritik des Epiphanius" supposed them to be even Philanthropists, on account of their denial of the Logos, and Epiphanius in fact calls Theodotus an apopasma of the Alogi; but this is only a guess, and is not derived by him from Hippolytus. As a fact, Epiphanius assures us (Haer. 51) that the Alogi (that is, Gaius and his party) were orthodox in their Christology (see MONTANISTS)."
Note that everything that was known (at least at that time -- there might have been documents discovered in the last century) came from one orthodox writer, who would have opposed them.