Found the answers in the Bar FAQ: https://beyondallreason.info/faq/what-are-the-differences-between-bar-and-zerok
TLDR: Zero-K and BAR are based on the same FOSS engine. Zero-K is less micro with better unit AI. BAR delivers a more vanilla and micro intensive Total Annihilation experience.
Supreme Commander is proprietary closed source and has some different mechanics. Larger but worse maps.
It must be playable for casual and single player gamers for sure.
I’ve never seen a casual friendly multiplayer RTS I believe. The FPS genre manage to do this, so I think it should be possible. Hmm… Nothguard, Dune: Spice Wars, Line Wars and maybe Total War. These could maybe be considered casual friendly multiplayer RTS.
Though I must admit I want a good e-sport RTS I can watch and maybe dip my toes in, now when SC2 and AOE both feel quite dead. It’s the only e-sport that really entertains me. (we’ll maybe chess is an e-sport as well nowadays)
As a millennial, I’m probably not alone when I write Red Alert, Atlantis, Diablo and Fallout 2 on a computer without internet connection. Also endless demos from PC Gamer CDs.
The more unusual game I want to add is Warlords 3. Got it as a Christmas gift from my cousins boyfriend (he was maybe 20 years older than me). Probably because he wanted someone he could play shared screen PvP with. Spent a lot of time with that game. The same guy also gave me a pirate copy of Diablo. I should probably give him a call today and thank him.
Also playing Tibia on a 33k dial up connection was special. A very laggy and expensive experience. Always afraid that mom would just turn off the connection because she had to make a phone call. And the true horror I felt when I encountered another player or a new monster deep within an unexplored dungeon. I didn’t like WoW when it came out. Probably because of emotional bluntedness that free PvP in combination with gear + xp loss causes.
And I’m still chasing the dragon.