To customize the darkrp entities, go to ch_bitminers_2/lua/darkrp_modules/ch_bitminers_2/sh_ch_bitminers_2_entities.lua
You can modify names, prices, maximum, etc.
If you want to make the entities yourself in darkrpmodifications then you can do that. Just delete the sh_ch_bitminers_2_entities.lua file and copy/paste the entities over.