u/Buh-Bye-Felicia

Do you think it would be smart or doable to trim branches from below to make these topiaries? These trees are at least 25 yrs old.

This holly has been in this spot for at least a decade with little attention. It's glorious, but taking up the walkway. I need to prune it, but how far back should I go? Will I damage her? Appreciate any advice.