If there are several rules applicable for the same product on the same position, will several related product blocks be displayed?
Starting from extension version 2.18.0, there's a possibility to disable several related products blocks in the same position. To enable this option, navigate to the general settings of the extension and turn on the Display Multiple Related Products Blocks setting.
In case the setting is set to No and there are several rules that are applied to the same product and share the same position, the one with the highest priority will be shown by default. The Priority value can be set on the rule configuration page in Catalog → Related Product Rules → choose the needed rule → Priority: