Does worldguard work for brooms too?

Yes, you can block the broom spell to prevent broom use.

But can you prevent players to ride the broom in certain areas?

Yes. /region flag whatever blocked-spells broom

Also wanted to ask you if for using this mod on a server w/ a different texture pack I have to change some blocks or particles and if it works along the conquest reforged mod

You would either need to merge the two resource packs, or else put example: norp in Magic's config file to turn on skull icons.

Thx for your help, btw the server's name will be WizardingWorldMC.
I'll let you know when it will be open.