I'm DMing my son and his finds during quarantine on Roll20. They wanted to try 2CGaming's Epic Legacy. We started at level and were playing twice a week, leveling up after each session. Wec started in Wildemount and they eventually each received a vestige magic item that scaled as they progressed.
First of all, they are closer on the the scale to min/max than RP but have loved it. Before that got to level 20, I was throwing monsters with up CR 25 at them. Once they got to level 21, I started using the Epic Legacy monsters, and incorporating the Qill and Caildron Ulraunt's Shadowfell and Acheron stuff at them. Then I finally got the 2CGanming Campaign Codex and added the Epic city of Nexus. I will say that the 2CGaming Epic characters far outshine most of the monsters. Plus trying to keep a sandbox storyline with Roll20 maps has been quite a but of prep work.
They reached level 25 last night, and combat is almost meaningless. There are multiple counter spells and even Wishes, epic Reverse Magic, plane jumping, time travel, multiple immunities and legendary resistances, Righteous Damage that is practically unstoppable, etc. As a DM, I have a hard time remembering all of the abilities of a creature I don't use often, especially with Legendary and mythic actions. I created a council of baddies: Arkham, Xanathar, Strahd, Dyrrn, Lord of Blades, Halaster, Acererak, Smaug, Zariel, the Timeweaver, even a clone of one of the PCXs (from the hag in Tomb of Annhilation) as a way of antagonizing them, but most of those guys are too weak now so I started creating my own monsters such as a Unicornado and a thessalchimera (hydra/beholder/illithid). And to balance, I really need more than 1 enemy so that just makes things more complicated. I try to keep things fresh so have various locations and environments (the cubes of Acheron, the "Inside of a Tarrasque," Avernus, Tomb of Horrors, etc. They are settling into a life in Nexus and creating their own (Epic Legacies) pantheon, but I'm not sure we'll make it to level 30.
They are already planning for a Humblewood session zero as a change of pace.