Freeza First Form (FNF) Runs the DBZ / DBGT Gauntlet:

[SIAD]

Can he against someone like Gotenks Boo, Gohan Boo, General Rildo Base?

 

[Diamond Ryan]

Didn't he one shot Ultimate Gohan? I think he should definitely be competitive with Gohan Boo at the least, though he probably loses to Rildo.

 

[SIAD]

I personally think that even Gohan in his prime didn't have a chance against Freeza First Form.

 

[Captain Cadaver]

He's stronger than Ultimate Gohan from the way Gohan treats him, though that's about as far as we have to go on and it's difficult for it to be by too much if Gohan flaring his Ki as much as he could was easier for Galu to sense on Whis' planet than Freeza's standing Ki. I'd say he'd be at best around Gotenks Boo's level.

 

[PFM18]

He's stronger than Ultimate Gohan from the way Gohan treats him, though that's about as far as we have to go on and it's difficult for it to be by too much if Gohan flaring his Ki as much as he could was easier for Galu to sense on Whis' planet than Freeza's standing Ki. I'd say he'd be at best around Gotenks Boo's level.

I would agree with that. I'd place him somewhere in the range of Super Boo and Buutenks. And then in his Final Form I'd place him either way above SSJ Vegetto or around SSJ Vegetto depending on how I interpret Buuhan vs Base Vegetto that day, I go back and forth on that.