In addition to the C&C remasters' campaigns, I've also had a good time playing with the games' source code. After years of TS hacking and patching with x86 Assembly, it's so much more convenient to use C and have properly documented code for the task.
My first objectives were to fix Red Alert 1's biggest issues, implement further QoL improvements and to get familiar with the source code. In the process I've also released a mod on the Steam Workshop that is, at the time of writing this news post, one of the most popular RA Remastered mods on the Workshop with over 4000 subscribers and a good share of positive votes.
If you wish for an intelligence upgrade for your Ore Trucks, generally better pathfinding for your tank blobs, and don't mind a bunch of other improvements, you might want to check the mod out on the Steam Workshop! Steamcommunity.com