It's basically the manga animated (with pretty good animation at that, aside from some low budget scenes which were corrected in the Bluray/DVD versions), only it does fix some small plot holes. But nothing really that noticeable and it's still a repetitive mess either way. Part 4 is better in...
Galu said that the Potara Fusion might be stronger if they turned SSJ before fusing. I guess this more or less shows that (as far as the manga/Z continuity goes anyway) Ultimate Gohan can turn SSJ with no power increase, because fusing in different forms might have untold consequences. Then...
Maybe they can't suppress their power to near zero after already fusing in a powered up state, like they can neither detransform nor power down further than the power they initially fused into.
I don't do DBS numbers so I just go by statements at face value unless they're hilariously stupid (like SSJ2 Trunks who's far above SSJ Caulifla who's above ToP base Freeza being compared to SSJ2 Gohan from the CG)
Beerus never noted his power went down and said Galu's power was supposed to be greater than Hit's. It was only due to the strain of constantly having to be .1 seconds behind and needing to account for that deficiency that Galu was tiring out faster. Same or similar effort that he used against...
I think Vegeta was much weaker than Galu prior to gaining SSJ4, especially ascribing by the theory that Galus lower forms (base especially) caught up to his SSJ4 form over time.