Hi @pau,
I don't use much deblur myself, but I would start following the tutorial linked above. The chimera filtering should be included as one of the deblur step (as well as within dada2) so should not be necessary. There are many interesting discussion on the statistic beyond deblur (Deblur stats.qzv file meaning and interpretation - #3 by wasade), and comparing dada2 and deblur results (Different taxa result from DADA2 and Deblur). So please search also the forum for more information.
On the quality filter, from the manual: the default for the quality-filter q-score=4 (q-score: Quality filter based on sequence quality scores. — QIIME 2 2020.8.0 documentation), in the dada2 denoise-single: the default is 2 (denoise-single: Denoise and dereplicate single-end sequences — QIIME 2 2020.8.0 documentation). So it seems even lower to me!
For the comparison, please consider that deblur pre-filter the sequences to exclude anything not loosely similar to 16S, so if you have other species in the samples, they will included into alpha-diversity results using dada2 but not in the deblur results. That may be misleading too!
Hope it helps