Reading values with HC-05 and sending commands at the same time working inconsistently
Actually got it working myself, but thank you so much for your help @chrisl

Ditched the for loop completely just to try things out and reorganized my code a bit. Surprisingly it started to work well enough.

Basically just moved my measuring stuff outside the while loop*(and now that I think about it, why would it ever be withing the while loop? Literally makes no sense)* and to the end of the whole void loop part, and only polled for state changes within the while loop while the BT connection was active.

Doesn't miss a command as far as I can tell, and the adjustment is within 2 seconds when using my whole code, which is perfect. Also the whole program doesn't just freeze itself while trying to think what happened when the change set was send.

Here's a short version, should somebody bump into this thread in the future.

void loop() {
   while(Serial.available() &gt; 0){       
    state = Serial.read();              

  if (state == '0') {stuff happens here,
    }
    }  //End of the while loop.

  sensors.requestTemperatures();
  delay(1000); 
  Celcius=sensors.getTempCByIndex(0);
}