Currently have Optimum (Suddenlink) cable modem/internet. It's fast enough (100 mbps) for our needs but not stable and way too many outages. Looking at switching to 1Gb fiber supplied by our local telephone company. Yes, they still exist. I can buy a modem/router supplied by the telco for $85 or supply my own PPPoE compliant modem/router. I know nothing about this subject, so no idea what the benefits/advantages are for having my own equipment vs telco supplied.

Modem let them supply, you provide a router behind it imo. A mesh unit setup i recommend 2-4 units depending on house size. If theirs is a combo modem/router, just have the router portion put into pass through mode during installation.

Reason i recommend their modem is so they can perform diagnostics remotely on it while your router for security and performance.

if you're looking for mesh a lot of folks here like ubiquity

Tell them when scheduling your install "I have my own router. If possible I would like a modem only from you (telco) not a combined modem/router."

Just be prepared and ready to set up and configure your router as soon as the installer arrives.

How involved is the setup of a typical router?

May want to look into a mesh system. I have a 5G WiFi extender that seems to be on its last days. Our house is a little over 2400 sq ft. It's a split level with open living, dining and kitchen on the main level. Living/dining area has 16 foot vaulted ceiling. There is a small office nook off the living area plus 1 bath and 2 bedrooms on that level. There are 2 upstairs bedrooms plus a bathroom, directly above the main level bedrooms and bathroom. The WiFi extender is upstairs on the landing outside of those bedrooms. Downstairs is a former playroom, now man cave and one bathroom. This room is under the living/dining area. The current cable enters through an outside wall into the office nook. That's where the cable modem is and like where the new modem/router will live. There is no garage, only a carport at street level with an attached workshop. It would be nice to get WiFi in there. How do you determine the mesh system components required and is there setup required using a PC, or could I maybe use my iPad?

Get a mesh system. Those range extenders are garbage and harm your coverage more than help it. I have been really happy with our Eero mesh system. Did all the setup on my phone.