If it was me and I was going to use all the existing wiring for possibly 4 new Wyze cameras, the easiest way would be to use something like this 10 amp 5v supply in the link and connect the 4 way splitter directly to that power supply. At 10 amps, that would in theory be able to supply 2.5 amps to each camera which should also be enough to overcome any loss from the wire length to each camera. Then you would just have to decide on which USB connector to put on the camera end of each wire.
This one would work in the basement with the 4-way connected to it:
And then this on the camera end should work and be plug and play:
You would just have to verify that your plugs are indeed the standard 5.5X2.1mm
With those options, the only cable cutting involved would be to connect the 4-way splitter to the power supply and add an AC power plug to the power supply.