It's impossible to understand the chain rub from what you describe. An experienced cyclist would be able to work it out straight away, which is why you'd do best to go back to the shop, explain why you're disappointed and ask what they suggest needs to be done.
I'm dead against the notion of "servicing" a bike. With a car, yes, oils and filters need changing and sometimes brake pads but there's nothing an owner can do routinely to keep it running smoothly. A bike is different; parts wear fast, cables fray, wheels get damaged, it's an assembly of delicate mechanisms attached to a frame. A competent cyclist is on top of all these adjustments and doesn't leave them until one big service or worse, leave them to some muppet who has no experience of the bike or emotional interest in it. At any time a good cyclist would be able to tell you the condition of their tyres, brakes, cables etc. without even looking. When something is less than perfect it gets replaced or overhauled. The French manufacturer Mavic makes very good wheels but they are designed with a certain engineering philosophy in mind and if the owner doesn't maintain the freehub it dies within a few thousand miles with a horrible howl of death.
There's a good explanation on brake adjustment above. It's about setting the pads so that braking stress pulls them parallel to the rim.
There is nothing to fear with carbon bikes. Carbon is stronger structurally than other materials but more easily damaged by careless handling. They are massively popular because they're light, structurally stiff yet smooth-riding and feel fantastic to ride. If you have concerns sign up for the Cyclist magazine track day near you this spring and spend an enjoyable day riding all the top carbon (and some aluminium) road bikes. I guarantee you'll be blown away. My BIL, a dyed-in-the-wool steel touring bike rider came along with us to York last year, tried a Specialized Roubaix, bought one the following Monday and now loves it, saying it has even taken 2 mph off all his average speeds.
Here:
https://www.cyclist.co.uk/news/2650/cyclist-track-days-2019-buy-your-tickets-now