I see that we need to work on our language.
The origin of the instruction in Category: Congregationalists to place individual Congregationalists in a category for their local church does not reflect any decision that religious professionals could only be categorized on the basis of church organizations.
The origin of the instruction for categories ending mostly in "ists" is that these categories have been set aside as a type of category we call a personal faith category. It all started when people were using these categories as both a high level category for the top of a religion's structure of categories and also as a default category for profiles where the religion of the person was known, but it was not known what particular local church the person and family belonged to. Using the same category for two different purposes was the cause of a lot of the tangles we had in the religious categories that we were trying to solve.
The most common reason for putting a religious category on a profile is that members of the same family are often of the same religion and attended the same church. But when the particular church is not known, people still wanted and insisted on using a category to park the profile in for the religion until further research was done and a narrower category became a better fit. So that is the purpose of the personal faith category.
We need to be clearer as to what the purpose of the personal faith category is and that neither it nor a local congregation category is intended to preclude the use of other religious categories but rather that the personal faith category is a substitute for a narrower local congregation category when the local congregation is not known. However, a personal faith and a local congregation category which includes a personal faith should not both appear on the same profile.
Religious Occupation categories for particular religions are intended to have two lines distinct lines of parent categories - one in the Occupations stream under Religious Occupations where the category names are ordered so that the general list will be sorted by broad religious categories and one in the Religions and Spiritual Traditions category for the religion so that religious professionals can be found either by their religion or by their occupation. We just are not there yet in linking everything up.
There is actually a third line as well. All the categories under Religious Occupations are also repeated under Religious Figures and Religious Occupations where the focus is on the role each person held within their religion. All the existing minister, priest, and other religious occupation categories will appear through all these routes.
The sudden inability to find relevant categories for these people anywhere in the WikiTree category hierarchy is because I just started working on implementing all the different paths to these categories and I don't get to spend enough time on Wikitree to do it quickly. I have submitted to Editbot the move of all the categories under Religious Professionals to under Religious Occupations. That action did make them harder to find for the moment. It is such a large group of categories that it will require Aleš' personal approval and attention before the move is completed.
Please be patient with me and the Categorization Project. Restructuring takes time. I also have to spend time on other areas like being coordinator of Project Denmark. An issue with categories there has taken me away from the Religious Categories for a few days.
There are some general categories to serve the purposes you describe, but maybe not as many as we need.
There is a line of missionary categories which are grouped primarily by where the missionaries had their missions. There is also a category for Evangelists. As evangelist is defined as a person who seeks to convert others to the Christian faith, especially by public preaching, perhaps that is where Lorenzo Dow fits.