The risk comes from taking the 2b agonist regularly, that's why it causes fibrosis. Not only is taking the larger dose safer as long as there are no preexisting cardiovascular issues but microdosing has been shown to be no better than placebo
Microdoses also don't inspire hippocampal neurogenesis whereas larger doses do
Microdosing is not only not beneficial but it may be actively harmful
"...it is possible that chronic microdosing may carry a risk of fibrosis and VHD, which should be assessed in future studies. There is converging evidence that simulation of the 5-HT2BR over several months may lead to the development of fibrosis. Duration of intake plays a major role in drug-induced VHD, even if the substance is not taken daily (Connolly et al., 1997; Schade et al., 2007)."
Microdoses also don't inspire hippocampal neurogenesis whereas larger doses do
Microdosing is not only not beneficial but it may be actively harmful
"...it is possible that chronic microdosing may carry a risk of fibrosis and VHD, which should be assessed in future studies. There is converging evidence that simulation of the 5-HT2BR over several months may lead to the development of fibrosis. Duration of intake plays a major role in drug-induced VHD, even if the substance is not taken daily (Connolly et al., 1997; Schade et al., 2007)."
https://journals.sagepub.com/doi/full/10.1177/02698811231225...