You can set up a list based on company size as long as that's a property you're tracking, yes. Then, in HubSpot, you can send emails to Contacts from the Contact owner, so you can create 1 email that covers all of your reps.
You can also create a list that segments all the Contacts associated with a Company that you designate the criteria. Example below is based on total revenue, but it would work the same for company size if you're tracking that.
So in short, you will be able to accomplish what you're look for.
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