I think the resistance "welding" is what a person from Switzerland I know told me he took some courses to learn.
I assume the difference between soldering and resistance soldering is the method to produce heat. Higher resistance creates more heat where a soldering machine increases the wattage (amps) of an electrode to increase temperature of a soldering iron tip.
Googling "How resistance soldering works"
Resistance soldering as the name suggests relies on the resistance of the solder to the flow of an electric current to generate enough heat to melt the solder. This occurs in exactly the same way as an electric radiator or incandescent light bulb worksGoogling "How does resistance welding work"
Electric resistance welding (ERW) refers to a group of welding processes such as spot and seam welding that produce coalescence of faying surfaces where heat to form the weld is generated by the electrical resistance of material combined with the time and the force used to hold the materials together during welding.
Welding your melting metal with penetration whereas soldering is more like brazing materials.
So regular soldering and welding are similar with the latter penetrating materials. Some forms of welding such as MIG has no Amp (wattage) setting. In order to increase amps on a mig welder you increase the wire flow rate, more wire = higher amps while adjusting voltage.
I've done both stick and some MIG and mig is related more to speed. Less time is normally used to create a weld, as you can't hold the wire and work a puddle as long as when stick welding.
My Hobart MIG welder adjustments. Takes a while to get the hang of mig welding, it has some advantages over stick.
1 Voltage Switch - Use control to select the weld voltage range. As the thickness of material increases, a higher voltage range must be selected
2 Wire Feed Control - Use control to select a wire feed speed. As Voltage switch setting increases, wire speed range also increases