The main steps of connecting to WIFI are scanning (channel), authentication, association, and DHCP. Some users who use the LWIP protocol stack may also have an operation to detect IP conflicts.
In the scanning phase, the channel can be recorded after the first search, and the channel will be scanned first next time. This method does not achieve good results for some routers that frequently switch channels automatically.
In the authentication stage, the small device calculates the PMK (pairwise master key) based on the password and the WIFI name at this stage, which takes a lot of time and can be calculated and stored in advance for the next use;
You can consider using static IP during the DHCP phase if conditions permit.
Some LWIP protocol stacks will detect whether there is an IP conflict after applying for an IP, which takes about 1 to 2 seconds. This function can be turned off.
I have done some testing and verification before, and the above are several major aspects, but I can’t remember many details.