I just turn the quality on low and disable weather, that makes the game run pretty smoothly on my computer.
As for the lore, there's an in game timeline you can follow now! In each of the tabs in the book of lore (the scroll on the bottom of the screen) there should be a link to the timeline which links you to the quests in their "proper" order, it gets a bit confusing in Book 3 because there's so many plots but it'll help you figure out the basic locations/people to talk to to progress the "story." If you have a certain class you like to play as you might want to b-line there first to grab that so you don't have to wait. There's also a lot of quests that aren't on the timeline that you can find just by poking around towns and exploring the map along the way.
Also this is something that confused me when I came back to the game after a few years: The seasonal events are sometimes tied into the plot and some characters/plot points will be introduced during these, leaving a hole in the timeline when the event isn't available (unless you have the book that lets you access them year round). Similarly if you decide you want to take advantage of a seasonal event book being available (it's Mogloween now!) know that you'll likely get some form of spoilers if you aren't all caught up.
Also the Inn at the Edge of Time is super cool but really hard and ultimately optional.