dont overthink the program part, just pick a program and go with it.
overthinking a program usually ends up in being not fully committed to the routine. I.e if a day doesnt go well or a week is off your more likely to 1. not finish the program or 2. start the habit of program hoping mid routine which is a bad thing
my best advice for program picking is take a well known routine that is known to work (5/3/1, different type of intermediate 5x5 routine, cube, etc. )for others and commit to a full cycle, thru ups and downs. think of it this way, if you put full effort into a program ,at worst you can say you put 100 percent in to and it didnt work and then move from there
also i say to look for another 5x5 routine because it is relatively known that ed coan,even in his world record time, would use sets of 5(main and aux lifts) up until his peaking routine.
personal experience tells me that since 5x5 worked for you it might be a good idea to run another program for a while and then try another 5x5 routine when gains stop happening because people ive been around have 2 responses to 5x5s. 1. doesnt work at all 2. is something that they can come back to from time to time to get surefire no doubt about it gains on their lifts