Do I need other EP to play B&H to the fullest?

To the fullest, probably yes.  Here's an article on all the cross pack features for Businesses & Hobbies,

https://simscommunity.info/2025/03/05/businesses-hobbies-cross-activities/

Yes and no

No because you can have loads of possible businesses without additional EP. You can own a pool, bar, cafe, shop, tattoo parlour, art gallery, gym,... and many possible combinations of base game activities. There should be a lot to do with just this pack

Yes, because packs will give you even more options like run a pet cafe, spa, laundromat, occult cafe, .... There is a lot of pack integration. I look at it as a little extra for people who own more DLC, not as a requirement to enjoy the pack.