hardware issues / SMC reset: keyboard, trackpad, flickering screen
You have a hardware issue - possibly two - and you should take it in (back) for service.

The two issues: flickering on the screen and trackpad/keyboard issues are most likely coincidental and have nothing to do with each other.  Given that you just had it in for service on the screen and it's showing issues, I would've taken it back already.  

The SMC reset really has nothing to do with any of this.  The SMC is just Apple's name for the what the rest of the industry calls the PMU or Power Management Unit.  Resetting it just sets the sensors, counters, watchdogs etc. back to "zero."  The SMC just regulates where power goes and how fast to spin fans based on data it gets back from the rest of the system.  

The fact that you have intermittent failing haptic feedback, an unresponsive cursor and a failure to connect to either the keyboard/trackpad, indicates there's a hardware issue.

If it appears  SMC reset "fixes" your problem for a little while but then it returns, there's a good chance there's a power issue like a faulty component (resistor, capacitor, etc.) but in the end, the item needs to be serviced.  Chances are, you'll need a new top case assembly.