Random bufs are not so much a problem, the chances are low but it is nevertheless possible to get invincibility and dmg buff and even 100 fury at the desired partner
Modes are useless except 1 and 3.
B Urahara is the fastest partner in ubp for now so f2p and low vip lvl players will probably put all speeds on him and their assaulters will be slow
so there is a big risk if you use B Urahara when you fight against an opponent who can ignore invincibility, your attackers will be slow and useless unless if you have assaulter like muken who can survive first round and one shot all or ks to clear all debuffs from enemy team.
It is desirable to have a muken or a raijin for a combo or a ks for debuffs.