ESP8266 + Logic inverter on Tx = Failure to boot ?
I have the same problem. In my case, on ESP8266-01S I use Tx, Rx as input, GPIO0, GPIO2 as output to control 02 DYI SSR relay together with 02 TTTP223 touch module.
If Ttp223 I/O pin would be connected to TX pin, ESP8266-01S wont boot, if i remove the one connected to TX then it boots up normal. After the boot, pluggingin of the TTTP223 will work.
After sometimes, I found that TX is must be HIGH for normal boot, when TTTP223 connected directly it will pull the TX down to LOW and causes ESP to stop normal boot.
I did a small tweak for only TX pin connected to TTTP223 as following:

Make a 3.3K pull_up to VCC for TX (IO1), let's call the I/O pin on TTTP223 as IO2;
Use any NPN transistor to handle with following schematic:
IO1 &gt;&gt; Resistor (470 Ohm) &gt;&gt; Collector,
IO2 &gt;&gt; 1K &gt;&gt; Base
Emitter &gt;&gt; ground.
Then all work just fine, normal boot and touch module work as well.
Note: This problem only happen with TX pin but not RX