Re: Log too big?
Well, I have a fairly fast Win10 machine with plenty of RAM, yet when I switch from "Last 50" to "All" it takes 13 seconds to display the data. I have about 24,000 records in ACLog. I can see how this would delay showing that your FT8 QSO had been successfully logged. Obviously, ACLog has to do a lot of work each time a change is made, including logging a new contact, when you are displaying that many records.
I'd say you have three choices:
1) As KD5KC (great suffix, Mike!) suggests above, invest in the fastest machine you can and stop all processes you don't need so as to save RAM, or
2) Accept that it will take ten to fifteen seconds for WSJT-X to confirm that you have successfully logged the FT8 QSO, or
3) Keep ACLog on ""Last 50" and do the database housekeeping when you are not logging contacts.
Note that I did not suggest trying other logging programs. I suspect you'd see similar behavior with most (if not all) and, more importantly, there are none as good as ACLog...in my humble opinion.