When it comes to how a church does missions
In my experience, the easiest way to understand what a local church does in global missions is to ask the question, "How many people attend the church?" That one question usually indicates what the church does globally. I realize that this question can sound a bit, shall we say, unspiritual. But let me unpack this for you before you write this concept off as flakey.
I call this model the "RSM Model" where RSM means "Relative Size and Maturity." As a church grows, they go through different missions approaches based on their size and how mature their understanding of global missions might be. For sure, you can find huge churches with immature missiology, and you can very small churches with a mature missiological outlook. Some of the most impactful churches are those that break out of the RSM pattern. But, generally speaking, the RSM model lays out a general pattern about how churches do missions.
A few other disclaimers I would make:
Not all churches progress through this at the same pace
In no way do I see the "large church" on the right side of the chart as the goal - one might argue that churches between 800 and 1,500 people are, in fact, the most actively engaged global churches by size
There are advantages and pitfalls at every stage of this chart
Just one person can change the paradigm in a local church
With that background, this is how I see church size affecting missionary outlook at the local level:
There is a lot to unpack here, so let us just take one row of the chart and I will explain it. Church Missions Staffing at a small church is typically the domain of a missions activist from the congregation. In a small church, so much is needed from the pastoral staff (usually just one or two people) that missions is lay-led. As they grow, churches most often appoint somebody to be the "missions person" on staff. Usually, this is the finance administrator (because missions is mostly a financial investment) or the youth leaders (because missions is short-term teams). Big changes happen when a full-time missions pastor is hired. This is when the church develops its own strategy and begins to ask others to conform to it (for example, financial support requests are passed through a rubric of some sort). The largest churches have entire staffs dedicated to global missions. These staffs have a specialization (for example, a region of the world or a particular type of ministry like Business as Mission). Each of these staffing changes brings a different approach to how the church does global missions.
Following down the chart one can observe different aspects of how churches "do" global missions. The presence of a missions pastor, though, is probably the biggest single difference between the left hand and the right hand of the chart. It is a fact that before the 1980s, very few churches had full time missions pastors. This is a recent role in the local church and one that affords great advantage to churches that staff this position.