I'm also in the process of buying a home for the first time, and did some search on Trulia/Zillow. It was OK, but the data gets really stale. One home was sold already before it was taken down. I did find out that Houston has a really nice site, har.com that lets you do basically everything Trulia & Zillow does. Realtors have other interface(s) into the same data, which lets them do different things like N sided polygons instead of just squares for map searches.
Tours vs images is definitely an issue. Some people are just bad photographers, some only have 6 images (Houston MLS requires 6 images for a posting). Some are good photographers, that make things look bigger than in person.
Experience is hugely variable though. I called 2 agent offices, and got stuck with their most inexperienced Buyer's Agent. The more experienced people are doing sales of homes or commercial, and getting a cut of the commissions of the people under them. Some Googling led me to roughly a 60/40 split between agent & office, along with the agent paying a desk fee (~$50/monthly). Since the principal is still getting paid, you can involve them if needed for second opinions or more nuanced explanations. Agents are getting roughly 3% of the sales price.
Still read all your documents. I've caught things that slipped past my realtor, and also brought up questions for her to answer.
Inspections are a mixed bag. They have a preferred list, and should also provide you a legal document stating their incentives for any recommended providers (including home warranty companies). I ended up going with one of my realtor's preferred inspectors, but only after calling all 5 on their list, and several more listed on Yelp.
Knowledge goes back to experience. My agent was basically bowled over by 2 of the new home builders in the area. It was so bad I considered buying the Realtor's Residential Construction Certification program (1 day course, ~$300, they'll sell to anyone) and going through it myself if I went with new construction.
Another point about knowledge is that even with experience, you can come up with stuff they don't know. Neither my agent or the broker (my agent's boss) had worked with anyone that negotiated their lender origination fees. I got $500 off one lender and $1000 off another.