SC/LC & Y/M in USMS competitions

I couldn't find this question answered on the USMS site, so here goes.... What's the mix of courses in USMS competition? I take it that Nationals are always LCM? Below that, are there general trends I should expect to see, e.g. mostly SCM with some SCY but few LCM? The reason I ask is that I want to know how best to train, especially if/when to spring for a membership where I can use a SCM pool (my gym is SCY), altho I'll probably do that anyway at some point b/c the gym pool has no blocks. :( I'm also curious about others' experience with training SC and competing LC. There are some LC pools in the "big city" nearby, and perhaps I could do some training there as I get closer to having to compete LC (which hopefully I'll do eventually). A rather open-ended post, I know, but any information is helpful.