Regarding specific weapon locations you can try this Nintendolife guide: www.nintendolife.com/news/2018/06/guide_hyrule_warriors_definitive_edition_-_all_weapons_and_how_to_unlock_them There used to be a video around on RU-vid detailing weapon locations specifically for the Definitive Edition but it mysteriously disappeared. I personally do not memorise where every weapon is though I remember some key ones but generally from now if anyone wants to know where a specific weapon is I expect them to check that link. It may or may not have some errors where locations were changed since Hyrule Warriors Legends. If anyone finds a better guide feel free to link me to it. The game "sort of" shows you where all the weapons are; you simply check for a character/weapon icon on the adventure mode maps which should also show the level of the weapon (eg; LV3). This will match the weapon's place on the respective list per character in this video: 1 2 3 4 4+. *8-bit weapons* I do not display them in this video as they are simply an alternative skin for LV 4+ weapons. You can toggle "8 bit weapons" on/off in your game settings.
The short version is focus on the story first as adventure mode progression is capped base on how far you've got in that. Most weapon/costume unlocks (and some characters) are from adventure mode maps.
Legends didn't have 8 bit weapons at all. Definitive Edition brought them back as a skin swap but technically they're just an alternative look for your 4+ weapons. The Wii U version is the only one that lets you get them as unique weapons in missions.
Going from memory, the story mode skulltulas on Normal and the first 2 Hard skulltulas (you have to beat the story to unlock them). You don't have to do the Cia/Linkle's Tale ones for that, and I think not the Wind Waker ones either.
