Community ball in BC (younger than High School) is almost always 3 down, Cdn rules. High School ball in BC is ALL 4 down NFHS US rules. Junior and UBC (Simon Fraser is still NCAA Div II, although after 30 odd straight losses they may want to reconsider) is 3 down Cdn Rules.
Long time lurker, and so I set up an account to correct some inaccuracies here.
All Community football in BC plays CFL rules. (There are a few differences for the younger kids, for example in Flag and Atom 2 points are awarded for a kicked convert and 1 for scoring by crossing the goal line. Atom, at least used to, play with 9 players per side on a narrower field). Community football is organized for kids as young as 6-7 (flag) up to 17-18 year olds (Midget).
All High School football in BC uses NCAA rules. Some kids in high school play both High School and Community but this depends on the coaches, many who do not let their players play both.
SFU does play in NCAA Division II, but their problems competing relates more to their difficulty in recruiting kids out of BC high school, rather than the quality of football in BC. From the kids I know personally who went on to play CIS, SFU is considered a disaster program administratively and they have not had stable coaching. Also, its not so attractive having to ride the bus to Arizona or California, most of these kids have travelled enough by bus by the time they finish high school. A big part of switching to Div II was to cut traveling costs. UBC has to use Air Canada or West Jet for all of their away games.
With all due respect, your "corrections" are not entirely accurate. Community ball in BC does NOT play CFL rules, they play Cdn Amateur rules as the two are significantly different. The variances you mentioned for Atom are known as "house rules" and are quite common in many cities across Canada.
High School football in BC use NFHS (National Federation of High Schools) rules, which are slightly different than NCAA, and I know this as I officiated in BC and did both 3 and 4 down ball for a few years.
Regardless, welcome to the forum. Look forward to further posts going forward.