Deleting Tags on Wordpress

#DELETINGTAGS on Wordpress. So I believe this is related to SEO. (Searched group but no info on this topic). Here`s the rundown: 1) Client has new website. 600+ blog posts imported from old site. 2) Client wants me to delete all 3000+ tags and re-tag posts. (Some tags have 0 posts associated with them bc the post was not imported) 3) Client Also wants me to edit 100+ categories - separate issue? I`m a little hesitant to do this! Questions:1) Anything I should be aware of before I bulk delete all the tags?2) Would removing them impact SEO? 3) Don`t tags help Google understand site structure? 4) Bad idea to remove tags when we are trying to rank a brand new site? 5) (Edited to add) Is this something I should do thru Google Tag Manager? Someone mentioned this tool in a prior post. I haven`t used it before. Thanks for any tips you can provide! Really appreciated your advice in the past!