This may the a NASA approved method laying 2 cables side by side lashing then soldering but you will never see me doing a connection or splice in that manor.
I've always been of the school to have a good electrical connection you must first have a good mechanical connection. simply laying the conductors side by side only offers a minimal amount of conductor contact area lashing with same type conductor material helps but still just barely offers more actual conductor contact Solder is for holding the cables together not the primary conductor. for side by side a far better connection would be to twist the conductors together for at least 4 diameters of the conductors this insures a solid mechanical connection even without solder but is not to be considered the final step in making a good splice solder needs to be applied to permanently bind the conductors.
For the end to end running splice on stranded conductors the strands should be exasperated or splayed open then put together as one would do the fingers of their hands Then the strands should be twisted in opposite directions and soldered
over the years I have found countless wiring harness problems in the automotive field where the splices were done exactly like NASA's shown method It only takes a momentary overload to heat a cable to the point of melting the solder which then becomes a hidden fuse in a loom or harness the conductor need not even become hot enough to damage the insulation before it fails
For crimp connectors I rarely use the insulated type or if I do I remove it before crimping then solder the connection after crimping re insulate and it is good to go
That's my opinion and it has worked for me since my very first vehicle