Provisional I hear you! I have said for years if I could get all the components of the game on all in one day, I could play with anybody. That day has never come haha.
There’s always something a miss. I did find a putter that flat out works, I rarely 3 putt any more, it’s all about distance control. A putt that’s slightly off line, but still finishes within 2 feet is way better than a perfect line but 6 ft short or long. I hit the practice green for a few putts before going out, all I worry about is getting the speed, from there, who cares? I won’t have the same breaks again on the course, might as well feel good about the control and move on. It has had the single biggest effect on scoring of anything.
Everything else is the same as you, one day it’s there, the next it’s not. Usually, if I focus on my basic swing cues, it’s easy to dial it in get to at least mediocre results.. which is to say, to my usual score haha. One the bag, just buy a lightweight bag to start and use it for everything, then all you have to do is pull clubs to be a “minimalist” or not. This is why I have the 3.5lb stand bag