i have read so many things that say that cedar mulch slowly kills plants

and shrubs by leeching the nitrogen and nutrients out of the soil.

There is no need at all to worry about this. ALL mulch sucks up some
nitrogen in the decaying process, but in good soil it's not enough to
concern yourself with. And once the mulch does break down, it actually
provides more nitrogen, so the only real concern would be when you
first put mulch onto new soil. I've never had a bit of a problem.

I would advise - as always - to not let mulch come into direct contact
with stalks or trunks of plants. Mulch is moist, and so can be a vector
for fungal diseases if it comes directly into contact with plants.