I'm sure there are other threads that address this, so apologies for re-treading that ground, but it seems easier to just ask than trying to dig that info up.
Started a playthough with the Level Up mod. Hit level 2 on the beach, level 3 after the fight at the grove gate, and level 4 after the ogres in the blighted village. I haven't looked at the spiders yet, not investigated Kagha beyond what you find at the grove, made hardly any progress into companion quests, and not even reached the windmill yet, to say nothing of the goblin camp, the teahouse, Waukeen's Rest, the Zents, or the Tollhouse.
I reckon I will easily hit level 6, if not higher, before I need to take on the Githyanki patrol.
*frustrated hand waving* Why is this capped at 4?
(Maybe the answer is "because spells/abilities at higher levels aren't fully implemented yet", but that's not really true, they're just imperfect; they lack descriptions or are replaced with feats)
(Also, I'm *biting* *my* *tongue* about experience coming overwhelmingly from combat, because I know that's been covered frequently. It's just lame.)