Combines Meshes to reduce Draw Calls then bad Lightmapping

Sorry for the bad explanation but I have tried to Combine the meshes in Blender (Control J) and also by using the Mesh Baker Unity Asset. The Draw Calls gets reduced and performance is really good, but when trying to lightmap again the result just looks so much worse than before combining.. Any advice to fix this would really be great! :)

I can see that I get fewer Maps after combining the Meshes (from 230x1024x1024 to 65x1024x1024) but nothing I can do about that as far as I know. I also tried to add a script to be able to use 4K resolution as Unity Lighmap has a max resolution about 1k, but wihout success..

So basically how to combine meshes the best way and get good lightmaps afterwards! :)

thanks!