[R-meta] Random vs. Fixed Effects model in metafor with multiple effect sizes per study

Good afternoon,
I?d like to run a fisher?s z meta-analysis with multiple effect sizes per study. As such, I have it set up in a multilevel framework. I have two questions:
1.Do I have to run it as a random effects model or can I run it as a fixed effects multilevel model?
2. If not, then I should run random effects model. However, when I run it as a random effects multilevel model I get non-significant heterogeneity. Is it still proper to run a moderator analysis when you do not find significant heterogeneity?
Please let me know if you have any insight on the best course of action to take!

My best,

Mia Daucourt