Wow, lots to update to keep in schedule.
So, handouts, those extras game master hands for players to make gaming more intense. My opinion in handouts is, that they are really cool, but actually unnecessary. I mean, you can easily just describe things or give a scratch about something. Still, if you dedicate time to make a cool realistic handout, it makes way better immersion for players about what their characters see.
Some possible handouts I have used:
There are maps in roleplaying games, but usually in fantasy settings these maps are tailored to suits GM's needs. To be frank, these maps are nice and comprehensive but if you think about game world, was cartographing so advanced that realistic and precise maps could have been developed? No.
For example distances can vary a lot for what they really are. Also some unknown or for the purpose of the map unimportant locations could have been excluded. So, hand drawn map for the players about the location as the game worlds inhabitant is more game realistic, than map what is made for the game material.
Instead of showing the map of whole game world for the players, draw a sketch how an inhabitant and cartographer of game world would have drawn it. It is more realistic than this full color sheet of precise mapping.
Instead of just telling what letter includes, I sometimes like to hand write the letter or use suitable font and print it. Sometimes if letter is older, or in bad shape, I might burn it's borders with a lighter or wrinkle it to make more worn out look.
It does not need much effort to write a letter instead of just describing the words. And if you draw, even a simple, seal it looks more fascinating.
Also for modern campaigns news paper clips, documents etc. can be easily made.
Usually a map of a particular location might be enough. Sometimes though I like to draw or show a picture of the place. It can be copied from internet, or even a drawn sketch but it gives more atmosphere. For example, if characters are going to this ancient temple, show them a picture how the temple's entrance looks like from the outside.
Also, you might provide players a city map, but a picture about entrance with walls, market place or palace makes it more like being in there.
Verbal description is good and I usually take few distinct features and quirks of the NPC to make them unique. Sometimes though, if the NPC is an important person for the campaign or characters, it might be a good idea to provide a portrait for the characters. You can draw it if you are a drawer, or find suitable portrait from the internet. If portraits are smallish, it is also a good tip to put the portraits of NPCs on the table who are present at the time.
You can also draw of find pictures for items. Of course, like all other handouts you can describe this ancient witch lord's crown or magic sword of lightning, but giving a picture of item makes it more "real".
Basically, anything player characters see, you can make a handout about. Usually handouts might be related to present adventure, like letters or other important hints characters might find, but you can basically make a handout about everything characters see.
Still, don't overwhelm players making every single object and thing in game world to appear on paper. Just the most important and noteworthy ones to keep things simple.