Finding a spot on this team is very difficult, especially if you don't have Over in a Flash or at least bring some utility for Super Battle Road in the form of tanking or stunning. SS2 Cabba is at best a floater on this team and his Passive is not nearly as good since there are no other units from his category that are going to boost his chance to perform a critical hit. SS2 Cabba does at the very least have Shattering the Limit for [Golden Fist] SS3 Goku .
SS2 Cabba's Super Attack causes supreme damage and has no additional effect, his 12 Ki multiplier is 140%, which is not bad at all for an in-game unit.
Despite the fat that we already have Free-To-Play TEQ units with better Leader Skills, SS2 Cabba can still be used as a Sub-Leader for Dokkan Battlefield, but I wouldn't really use him anywhere else.
SS2 Cabba has quite a unique Passive, he receives an 80% ATK when performing the Super Attack, which equates to more damage with a support unit on rotation, and a boosted chance to perform a critical hit depending on how many units from the Universe Survival Saga you have on your team, including SS2 Cabba himself; the highest chance will be 49%, higher than anything that can come from the Potential System.
While SS Cabba is not a unit that we are realistically going to bring on either Super TEQ or "Universe Survival Saga", it cannot be denied that he is SS2 Cabba's best linking partner; sharing enough Ki links to automatically Super Attack even under [The Invincible Myth of Universe 11] Jiren's 2 Ki Leader Skill and activating both "Super Saiyan" and "Saiyan Pride".
SS2 Kale is a very good Free-To-Play support unit, she links very well with SS2 Cabba in terms of Ki, she activates "Super Saiyan" for him and her support Passive will greatly increase his Super Attack boost since they are calculated in two different moments.
"Tournament of Power", "Warrior of Universe 6", "Shattering the Limit" and "Golden Warrior" add up to 8 Ki: these are the links SS2 Cabba and SS2 Caulifla share in addition to activating "Super Saiyan" for each other, the only ATK link SS2 Caulifla has.
SS2 Kefla and SS2 Cabba link very well together in terms of Ki and they also activate "Super Saiyan" for each other.
Since you are realistically going to run this unit mostly on a Universe Survival Saga team, there technically no reason to invest in Critical any further than the natural lv.5; the ideal investment would be lv.15 Additional and either lv.6 Dodge and lv.5 Critical or lv.11 Critical. The Critical chance from the Passive and the one from the Potential System do not stack together and are rolled separately.
Should I use Elder Kais/Grand Kais?
Absolutely not, no Elder Kais/Grand Kais should be used to raise the Super Attack of this unit, even though the drop rate is not that high. This unit can be used in his SSR-UR state to raise the Super Attack of Honest Admiration Super Saiyan Cabba, the STR support unit, and will probably be used to raise the Super Attack of a future SS2 Cabba.