Insulation? Hard to say - there could be cellulose in the walls, there may not be... No way to know, visually; unless the seller's had upgraded insulation done. Even if there is existing in the walls and attic, it'll be pretty lean by today's standards.
An inspector familiar with the area will know the basic design of homes... I know in my area, there was a couple of pretty common plans built in the 50's and 60's - and major renos (like moving walls, etc) stand out. It's not fool-proof, but it's a start. If the basement's unfinished, it may also help 'tell the story'...
The house will likely be wired with 2 wire fabric-covered cable - it may or may not have a ground... It's far too new to have K&T. If there's 3 prong plugs, you may want to check a few with something like one of these:
»www.homedepot.com/h_d1/N-5yc1v/R ··· yJ7_C2So
If the inspector gets up onto the roof, it's trivial to see the condition of the shingles and number of layers - if they do the inspection from the ground, well, besides being a crappy inspector, they aren't going to be able to tell you much about the roof... 2 layers are allowed, but I've seen houses with 3-4 before, and heard of houses with more then that... If there's 2 or more now, and they are in rough shape, budget a strip and re-do.
I'm not much on plumbing, but galvalized supply lines are a problem, for sure... At 50 years, most plumbing will need some attention, to be honest - even copper will be showing it's age.
Yes, home inspections are visual, for the most part - but a good inspector can at least see signs that will tell you where you need to look further... An inspector with a background in the trades (electrician, roofer, etc) will have a leg up on someone who took their 2 day course, and - BAM! -are now a home inspector... I also recommend against using an inspector suggested by the buying or selling agents - they have 'skin in the game' - and have a motive for the house to sell. But that's a WHOLE 'nother conversation...