You can do whatever you're comfortable with. Some things can be a bad idea in general unless you have established infrastructure - free flaps, airway reconstruction, complex peds, cochlear implants to an extent.
Thyroids and parathyroids absolutely should not be sent to a tertiary referral center. I mean, general surgeons do it - how hard can it be? (Kidding....kind of).
The majority of general ENTs do pediatrics (up to 40% of a general practice from what I've read is going to be peds).
Types of common cases - FESS, septoplasty, tympanoplasty, neck node excision, biopsies of various things, thyroidectomy, parotidectomy, BAHA, tonsillectomy/UPPP, ear tube placement. That's probably 90% of what I've done so far as a generalist.