What was vegetto referring to?

[KyuubiAhri]

His Actual full power (ssj3) or was he suppressed as a super saiyan?

 

[Let's Go Fearless!]

Yup, he was referring his SSjin form especially how he was handling Boo.

 

[Zippy]

Its up for interpretation but probably ssj cuz hes obv not going all out as an ssj either

 

[Evil Vegeta]

Boo couldn't handle a playing around Super Saiyan Vegito. I highly doubt he'd be referring to anything other than his full-power in that form.