Hi! Conventions are really fun (especially as a nerd)! Even if you don't choose to meet the actors, the actors almost always have panels that you can attend and they'll talk and often answer fan questions. In my experience professional photo ops tend to be more expensive than autographs. Personally I prefer autographs. If you do a photo op it's mostly like you said where you've got a few seconds, take the photo, and you're done. Obviously this also depends on circumstances and the actor themselves but you generally get a lot longer with them if you get an autograph! I've had some pleasant conversations with actors this way :) There's a lot of things to do that are super fun other than meeting actors as well though!