What is the correct way to remesh? I'd like to remesh multiple merged objects into one mesh for sculpting. I've tried to do this with Blender's built-in remesh function, but it didn't work as I wanted. After the remesh, the shape had changed a lot, this visible the best around the short parts of the mesh. On the image, the left one is the original (converted from a curve) and the right one is the remeshed version.
Is there any way to preserve the mesh boundary and keep the shape after remesh? Or if it isn't possible what else can I do?
In this case Decimate modifier will be the best option for you considering that the remesh modifier changes the overall shape of your mesh , to reduce the amount of your geometry decimation can be best
Or if you want to stick with the Remesh modifier  you can increase the amount of voxel data to preserve the mesh shape