Where I have seen mulches up against plant stems be a problem most often was in unamended, or not well amended, clay soils, soils where too much moisture was held in the mulch becaise the soil would no absorb that moisture. The only way you will know for sure is try it, but many gardeners with soils that drain quite good do not seem to have a problem with stem rot from mulches too close to the plant.

I have not had any problems with using compost as mulch on tomatoes, peppers, onion, and spinach in my five years of gardening.

While I try to compost hot (as quickly as possible, up to 165F), an attempt is made to use finished compost. But in the end I use whatever is on hand.