You can modify the CSS gap property of the radio options:
import streamlit as st
st.markdown("""
<style>
[role=radiogroup]{
gap: 3rem;
}
</style>
""",unsafe_allow_html=True)
st.markdown("## Vertical gap for `st.radio`")
st.radio("Options", options=[f"Option {i}" for i in range(1,5)])