“If Anakin Died, Would Palpatine Get Use out of Dooku and Greivous?”
Palpatine obv wanted Anakin more, but if Dooku was a great number 2 to take him through the clone wars, he'll be a great number 2 until the next strongest apprentice comes along. But Greivous is a non starter for the empire.
He'll have a different skillset than Vader, likely with limited involvement in the military - taking a real keen hand with the imperial senate and making sure they're placated and eliminating any political threats + reconciling the seperatist worlds, so don't have to spend a lot of resources early pacifying them instead of solidfying and expanding. Dooku will be good as their dark side resources expand and help Palpatine gain power, but the margin between Dooku and the next strongest apprentice is going to be a lot thinner than Vader and the next. Dooku likely grooms an inner circle of dark side adepts much as he did previously.
Greivous will be killed - he was too valuable to pin all the heat of the seperatist crimes upon him, and while Dooku after surrendering and seeing the light as it were may be reincorporated into The Empire as he was "only" a political head who can potentially claim his heart was in the right place but the corpos and warlords like greivous stole the cause from him - and now he's ready to join Palpatine's new order for real change - Greivous fully represents the Seperatist enemy, and the republic/new empire won't be seen as the victor until he's destroyed.
He is useful as a general, war dog and jedi hunter - but once the empire is established, Palpatine will have an abundance of all three, and given Greivous's attitudes and combination of skills, who knows how he'd take the news of an empire defeating the seperatists, or palpatine as emperor given he fought them for so long. he would poise the strongest military threat early on if left unchecked, and even if he wouldn't do so - the mere capability is enough to destroy him
in the original timeline Palpatine shuts them down because while they're not undefeatable, they can be an early challenge in a developing empire - particularly if Greivous is kicking around still to have a grudge and command the remnants
So basically, Dooku would be useful and Greivous would be destroyed.