To expand on Kevin’s answer. Unlike FCP, Premiere is pretty forgiving about format in terms of mixing footage in the same sequence.
Because of this “editing modes” like DSLR are just presets, just a bit deeper than sequence presets themselves.
The preview rendering format doesn’t mean as much because Premiere doesn’t smart render like FCP does. Rendering in the timeline, normally, won’t increase the speed of your final render. The only exception to this is the “use previews” during exporting but these aren’t smart rendered either so you’ll get a generation loss from another cycle of compression. It does save a bit of time when rendering client drafts.
I recall there may be an exception to that, like if you keep your P2 footage all P2 through the course of the project/preview/export but I could be mistaken. I rarely work with AVCHD/P2/XDCAM
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