Thanks Dan!
I played around with the resampling and tried cubic technique rather than nearest, but it didn't seem to make any difference in the output raster. Also, I reclassified my slope % and most of my area falls within the 0 - 193% range, which agrees with the degrees visualization, per your suggestion.
I am still unsure of these results though, just because of the gridded appearance in the areas where the lowest resolution DEM was "stitched". I have circled it in the picture below. Do you think this is a reason of concern or am I overthinking this?
ps. thanks for moving my question, it is the first time I post on here!