Button " One click mining" is simply a graphic realization of the command "set generate true" . Let me remind you that the number of threads is calculated by the formula the amount of memory cache L3 divided by 2.
You are quite right. Any Qt-wallet is mostly graphic realisation of the rpc commands for any coin. The boost manual recommends to use thread count less or equal number of cores. We use
standard bitcoin algo to check core count with Boost.