try to fix speed/latency issue

Firmware/configuration/mega2560/Configuration_adv.h

@@ -445,7 +445,7 @@
  * Enable Autotemp Mode with M104/M109 F<factor> S<mintemp> B<maxtemp>.
  * Disable by sending M104/M109 with no F parameter (or F0 with AUTOTEMP_PROPORTIONAL).
  */
-#define AUTOTEMP
+//#define AUTOTEMP
 #if ENABLED(AUTOTEMP)
   #define AUTOTEMP_OLDWEIGHT    0.98  // Factor used to weight previous readings (0.0 < value < 1.0)
   // Turn on AUTOTEMP on M104/M109 by default using proportions set here
@@ -1089,7 +1089,7 @@
 
 // Slow down the machine if the lookahead buffer is (by default) half full.
 // Increase the slowdown divisor for larger buffer sizes.
-#define SLOWDOWN
+//#define SLOWDOWN
 #if ENABLED(SLOWDOWN)
   #define SLOWDOWN_DIVISOR 2
 #endif
@@ -1305,7 +1305,7 @@
 #endif
 
 // Change values more rapidly when the encoder is rotated faster
-#define ENCODER_RATE_MULTIPLIER
+//#define ENCODER_RATE_MULTIPLIER
 #if ENABLED(ENCODER_RATE_MULTIPLIER)
   #define ENCODER_10X_STEPS_PER_SEC   30  // (steps/s) Encoder rate for 10x speed
   #define ENCODER_100X_STEPS_PER_SEC  80  // (steps/s) Encoder rate for 100x speed
@@ -1995,7 +1995,7 @@
  * NOTE: This method is less reliable as it can only catch hangups while
  * interrupts are enabled.
  */
-#define USE_WATCHDOG
+//#define USE_WATCHDOG
 #if ENABLED(USE_WATCHDOG)
   //#define WATCHDOG_RESET_MANUAL
 #endif
@@ -2348,13 +2348,13 @@
 // For debug-echo: 128 bytes for the optimal speed.
 // Other output doesn't need to be that speedy.
 // :[0, 2, 4, 8, 16, 32, 64, 128, 256]
-//#define TX_BUFFER_SIZE 128
+#define TX_BUFFER_SIZE 128
 
 // Host Receive Buffer Size
 // Without XON/XOFF flow control (see SERIAL_XON_XOFF below) 32 bytes should be enough.
 // To use flow control, set this buffer size to at least 1024 bytes.
 // :[0, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048]
-//#define RX_BUFFER_SIZE 1024
+#define RX_BUFFER_SIZE 32
 
 #if RX_BUFFER_SIZE >= 1024
   // Enable to have the controller send XON/XOFF control characters to