Do I need to brace joists after removing basement ceiling?
I think the terms you want are blocking or bridging or cross bracing: connecting adjacent floor joists together to keep them from twisting and warping.  This common, even code mandated, in new construction.  In seismic zones these can be necessary to prevent racking of the floor in an earthquake:



Chances are you already have these in your 1908 structure.  Removing the lathe ceiling will reduce total bracing somewhat, and increase potential for twisting.  But I rather think that after 100 years the joists are hard, dry and have done whatever twisting they are going to do.  In new construction, often done with wet lumber, twisting is a far greater issue.

I'd question the need to remove the old plaster and lathe.  As long as the knob &amp; tube wiring is under-amped there is no technical conflict with blow-in insulation (there may be a code conflict, relevant or not for you).  And that's far easier, and far less messy.  Wireless technology can be used to achieve certain electrical goals without new wires.