Fast Attack
Now it is the 10th Edition of Warhammer 40,000. Although Death Guard is the codex of choice for most Nurgle players the regular Chaos Space Marine Codex also has Nurgle in it, as the does Codex Daemons. It is possible to build a Chaos army using four books and I may finally get around to do that. Fast Attack may no longer be a concept when selecting your army. But it was in previous editions including 9th when we organized the Siege of Vanithro's Bastion Crusade.
Chaos Spawn
The link above does a pretty good job of explaining how I painted the first one. I plan to paint more and ened up painting four. I like big squads especially for models that are cheap and have no guns so no reason to stop advancing. I may even use one of the new Beast of Nurgle models but there is actually a lot of variety in the Chaos Spawn kit.
Inconceivably at some point GW made Beasts of Nurgle fast attack, but GW giveth, GW taketh away as now they and even worse Nurglings are only in the Daemon Codex. You can field them depending on which version of the rules you are using and I had to rebase mine twice, because the rules keep changing.
Briefly there was a time where Nurgle renegades could both have heavy weapon troopers and dudes with jump packs and bikes. I used to use Nurgle characters at least with both jump packs and bikes extensively in 2nd Edition. Now it is eight editions later and I'm not even sure I played them all, but depending on what the as yet unreleased newest Chaos Space Marine Codex says I may paint up two more bikers to go with Isaacous, I also want to do a squad of Nurgle Raptors so I can use more old models. Most people seem to love Raptors with an icon or without, but I've always been a contrarion and I need anti-armor more than assault troops, you cannot have Raptors if you stick with just the Death Guard Codex.