Can this be done?

Yes. Please include a sketch of your proposal to confirm.

[2832's?]

The lengths or the number aren't the design criteria, exactly, but how many are let to be on at any time.

That's the crux of the matter - total current demand.

When specifics aren't discussed then worst case (the capacity for all ON, blazing white from each) has to be anticipated, my way of thinking.

A strip, or any number of strips,

*could be* run from Arduino 5V, so long as the total is not greater than 30 elements, I suppose (but that might be a strain - no guarantees).

Powering the WS2812 strips from a 5V supply all their own takes all that load off the Arduino 5V, eliminating all of the calculations and considerations, the fuss and bother, and leaves you to get on with the fun stuff.