The problem I'm having is that when I join 2 object and make them into one and continue sculpting as a result I start getting these blobs and won't connect with previous second mesh These were the 2 meshes that I joined (the upper rectangle one and the lower cylindric one). I intended for them to be smooth surfaces but their "geometry" is never connecting.
Let's say that you want to sculpt these two objects together:
First, apply their scale, then apply all their modifiers except Subdivision Surface that you just disable. Keep in mind that when you join objects, the last selected while keep its modifiers (and they will affect the joined meshes) while the others won't:
Join them with CtrlJ, then select all the meshes except one and go into Face > Intersect (Boolean) and in the Operator box choose Boolean > Union:
Set the origin of the object to its geometry, switch to Sculpt mode, enable Dyntopo, it works:
If you don't want to use a boolean workflow, consider joining and then remeshing specifically. Keep in mind that the voxel-sizes will need to be selected appropriately for the right level of tessellation to represent the surfaces you are working with.
It also helps if both surfaces used have roughly the same level of fidelity, though this isn't always essential provided the surfaces have a reasonable level of tesselation.
Joining and remeshing a low polygon object to a high polygon object makes inferring the volume of the objects not always work properly if the poly-counts differ a lot -- so sometimes you might want to subdivide the object with the lower polycount (especially if it was created using hard modelling or box modelling techniques -- and another was made of organic or sculpting techniques).