if my mechanic told me it needs o2 sensors but he doesn't do exhaust work. that would make me question everything.
exhaust work is cutting, welding repairing exhaust. sensors just screw into the exhaust pipe, I've never heard a mechanic say they wouldn't do o2 sensors. they usually throw those at everything. since technically they are a wear item.
I'd basically do a tune up if you haven't in a while, new plugs wires and o2 sensors. if you have issues from there you have a good base. that's not really throwing parts at it in my book since most people haven't changed any of that before and it's time anyways.
if you have access to an android phone. I believe torque app isn't iPhone, but they have others I'd guess, but this is a good cheap obd2 reader and 5$ torque app you'll be able to do some useful troubleshooting.
for Android Phones ONLY - Wireless Bluetooth Diagnostic OBD2 Scanner Car Code Reader and Scan Tool for All 1996 & Newer Vehicles ELM327 Compatible OBDII
https://a.co/d/9e6Qjy5