For Unity it might be a good idea to start with a 2D or 3D core as the URP and HDRP are quite weighty.
(Another trick might be to use an older version of Unity that has all the necessary functionality)
Its going to be a real challenge keeping the file sizes down.
I have a recent game jam that clocks in at 4GB on my machine but compiles to a 300MB game.
Even chunky prefabs can take up a lot of room.