How is this compared to the witcher 3?
It's really, really good. Both are fantastic games. If you like bows and arrows, stealth gameplay, setting up traps and planning your attack, you will love this.
Are the side quests 'quests' Or just errands?
There's a good number of side quests quests. There's also a good number of errands. You can also easily set up your own errands to help you find the materials you need for an upgrade.
Is the main character likeable in a way geralt and John Marston are?
Yes she is. I really enjoy how she reacts to the world around her, and how no non-sense she can be in specific dialogues.
Are the upgrades as satisfying as the Mastercraft ursine armor/swords?
There isn't a large variety of weapons, since you're mostly using bows and bow-derived stuff. The slotting mechanic does open it all up for customization quite a bit, and you can use any one of the available gear to take on the same challenge in diverse ways, it's quite nice. I do wish the outfit was more separated per parts so we had more control over it, but the current system works.
I know it's only early days with it but just a few quires and appreciate your answers.
It is truly a fantastic game. Combat is one of the best in years, the world feels very alive, the machine designs are awesome, and it is graphically stunning. If you like stealth, bows and arrows, and laying traps, you will love this game.