Many main contractors rarely do the work themselves. They subcontract electricians, tilers, plumbers, ceiling installers. So even if you trust the main contractor, the quality you get depends on the unknown people he hires.
Ask directly:
Who is your tiler?
Who is your plumber?
Who will handle wiring?
Request to meet them or at least see samples of their work. Write in the contract that specialized works must be done by qualified tradesmen, not random laborers. You’re paying for expertise, not experiments.
Your contractor may be trustworthy — but the subcontractor’s handwork is what you will live with every day.