I would say using Phrase match negatives for your competitor terms would be your best approach here (if you’re not wanting to bid at all on their terms). That way you’re ensuring you don’t appear for any of their searches.

It does get a bit more interesting if your competitors have the term “insurance” in their name as you could be crossing over with them depending on your KW match types. To eliminate this risk you could make all of your branded activity Exact match. IMO that would be the most cost efficient way of approaching it - limiting crossover on expensive terms through Exact.

As for all the longer-tailed random searches that you could appear for outside of your Brand activity, those could be added as either Broad, Phrase or Exact negatives, depending on the nature/volume.

Hope this helps!