Depends on the dragon. I don't expect the average adult to have a Bond villain lair. Dragons typically aren't architects, so they have to work with what's on hand. That might mean that their lair isn't perfect. Last I checked, dragons don't have a "find perfect master villain lair" power.
Same with henchmen. Sure it might have spies to warn it of encroaching PCs. And out in the boonies where this dragon is probably dwelling, it probably has access to orcs and the like. In other words, sufficiently capable, but not entirely dependable. Traps are likely if the dragon is able to force some kobolds into its service, but that depends on whether kobolds are local to that area.
I would hope that if the PCs are going after a dragon that they do their research. Learn as much as they can from those who've come before them. Maybe even find out as much as possible about that specific dragon if they can.
If they just decide on a whim to go a-dragon-huntin' then best of luck to them.
If the dragon is fortunate enough to have a hidden chamber to sleep in, then the treasure would indeed likely be there. I still hold that smart / lucky PCs are likely to encounter the dragon there however. Dragons are lazy creatures that love cuddling their treasure. Being smart doesn't make you flawless. As such, PCs hunting that dragon are most likely to encounter the dragon where it spends most of its time.
Which is why I prefaced my statements there with the dragon killing plans online here making assumptions about how DMs run dragons.
To me, the game is Dungeons and DRAGONS. Dragons are a very big integral part of my game (dungeons are as well), and in fact, the average adult or older dragon in my game does have a Bond villain lair. They've survived this long for a reason. Yes, younger dragons are tough, but if they make too much of a nuisance of themselves, there are always adventurous bounty hunter types to take them out. The adults are the ones that grew past that phase and realized that yes, humans, elves, dwarves, spell casters, etc. are dangerous, and unlike Smaug, the majority of my dragons take precautions. Serious precautions. The majority of my dragons also are the spell casting types since those are the ones most likely to survive younger age.
Other DMs do not run their dragons this way.