I did the following:
Smelt all lead oxide with copper oxides collected from the cupellation attempts, material was 22 kg, I added 1 kg sugar and some borax and soda ash, I got 10.5 kg of metal shots, then make cupellation for them in three equal batches, I used lpg with minimum air source, the issue was the high temperature of the cupellation furnace, copper can be oxidized easily with high temperature in cupellation process so the solution is to control the temperature and use a reduction flame during the cupellation process.
If I want to reduce the copper content by use an oxidizing flame, will PM's be lost in the oxidized copper, answer is yes, I did an experiment for some oxidized copper from the cupellation by parting it using nitric and at the end I got silver,gold and palladium!
I think the easiest way to get +99% copper from e-waste smelting is to use lead oxide and lead sulphate then make cupollation to reduce the lead content. Lead sulphate and oxide will push most of base metals into slags, but don't do that with tin, soda ash can take care of the tin.
Now I wonder if Copper electrolysis cell will be effected if I use copper-lead alloy about 50:50 , if lead is not soluble in copper sulphate electrolysis cell, that mean I can shortage the process and don't make cupellation, just melt lead-copper alloy into anodes and use it in copper electrolysis cell.