If I buy Season 1 Battlepass bundle, do I unlock anything when leveling up?

Accidentally posted in the wrong forum mate, you're looking for https://answers.ea.com/t5/Apex-Legends/ct-p/apex-legends-en

It's structured the same way as Fortnite according to https://www.eurogamer.net/articles/2019-03-18-apex-legends-battle-pass-season-1-roadmap-6014 . You can still get the 100 regular items in addition to your battlepass premium rewards so you never have to worry about missing out on any items (so long as you buy a pass at some point)