You can definitely hit max level while skipping those optional boss fights but I gotta tell you, you'll need to be pretty thorough with everything else. I learned this the hard way on my first playthrough actually! The main story gives you decent xp but the real juice comes from doing all those side quests and really diving into the dialogue options.

Here's what worked for me: i focused on exploring every nook and cranny, chatted with literally everyone I could find and tried to solve things peacefully when possible. Sure, you get a bit less xp from talking your way out of fights, but it adds up when you're doing everything else. Something interesting I noticed is that maxing out your inspiration through roleplaying actually gives you some nice bonus xp too.

Most folks hit level 12 naturally near the end of the game, but since you're skipping those optional bosses, you'll want to be extra thorough with the side content. I'd say aim to complete pretty much all the non-optional quests you find, and don't skip any chance for exploration. It might take a bit longer this way, but you'll get there just fine as long as you're being thorough with everything else.