What would be some good weapons and armor for a monster hunter in a lowish-magic setting? For context...

A gun. A VERY large gun.

Skallagrim has a good video on that

A spear is probably a good one. Keep it at bay.

>Doubt.

Plate makes it harder for you to hide, also most beasts like to bring you down before finishing you off, so I would rather go with cloth armor with a good collar.
Grossmesser is fine for humans but isn't optimal for stabbing and it's length becomes a flaw in a grapple and tight places, replace with a Messer.
Spear is fine but I would go with multiple, wingless, ones.
Axe is also fine as a tool and makes an adequate weapon.

Something made of iron.
Something coated in silver.
Salt. Lots of salt.
Things to write or draw holy symbols.
Fire.
Alcohol and food for bait, distractions, and offerings.
Any herbs and other plants you can find that are said to be used against the supernatural.

So instead of a Silver Sword, should Witchers take a Pick instead?
I don't keep up with the lore since my computer refuses to run The Witcher, but I know about there being different schools. Did any of them diversify in terms of equipment/magic?

Pikes. A longsword? Good luck getting that close to something with arms longer than your weapon. Bows and arrows? Probably not gonna bring it down before it gets in face-eating range. A shield? Not gonna do a lot of good when it's strong enough to break your arm through it.

But few monsters are equipped to deal with you and a few of your buddies stabbing it through the gut from 15 feet.

Depends on the monsters that are most common / dangerous

A single monster hunter:
>Light, durable armor(Plate backed with silk)
>Hatchet, Dagger, Rope
The rest depends on what you're hunting.

There isn't much info on that but the school of the Bear mainly uses heavy armor, Wolf and Griffin go for medium and the school of the Cat uses light armor, but those guys basically turned into hired assassins.
There is also the school of the Viper, who just work for Nilfgaard in exchange for their school getting rebuilt. They use medium armor too.

Lastly you have the school of the Manticore but even less is known about them than the other schools, they also use medium armor.
As far as weapons are concerned, they all have twin swords, but you can also get a crossbow from the Cat school.
I think most schools go for medium because heavy armor tires you out quicker and you need some stamina to cast magic.

The more I read into the witcher the more I realize that I only like it for its aesthetic thanks to the third game.

Btw, if anyone wants to riff on a specific set, the order in the picture is Manticore, Griffin, Cat, Bear and Wolf.

The two on the left are obviously the best ones, the others are "Edgy McMurderstab" "Fat Northerner" & "Wearing mail two sizes too small"

Assuming you're fighting animal like monsters, cloth padded armor with thick leather boots and gloves, maybe with metal backing around the neck and chest, if you didn't need to travel all that far. A small-ish shield and spear, with a broad bladed shortsword as backup, also usable as a tool. A short bow with poison for the arrows would also be useful if you can handle the extra weight, assuming you're hunting something that's not covered with scales or a shell.
If fighting numbers of armed monsters instead, like goblins or orcs, swap the spear out for a mace.

Feasibly they should take an axe of some sort with a spike. Enough momentum to cut it deep enough and enough heft for the spike to puncture.

Trick question, witchers are too busy being replaced by town guardsmen, professional dragon hunters and generally being too busy boning hot sorceresses all the time

Warpicks were notorious for getting stuck.

A bazooka and a flame thrower should do the job.