2 Beetle (1Sender/1Receiver over Bluetooth) and TX/RX

Before I order a bunch of Beetles i would like to know if the following works.

Sender:
1x Beetle BLE with Temperatur Sensor D18B20 inside full Metalbody HubMotor of Scooter (but distance to Receiver only 1m)
Send Temperature to Receiver via Bluetooth, nothing else.

Receiver:
1xBeetle BLE with IC2 Display (SSD1306AsciiWire.h), Buzzer, connected to a Scooter Controller over TX/RX Pads
Sketch without Bluetooth 20'000 bytes (63%), Variables 680bytes (32%) on Arduino Mini Pro which will be replaced with Beetle BLE
Receive Temperature from Sender via Bluetooth

Do i need any libraries for sending/receiving Data over Bluetooth?
Or is it just done with?
...
Serial.write(Temp); //send Temp
Serial.read(Temp); //read Temp

Communication with Scooter Controller:

#define XIAOMI_PORT Serial
#define RX_DISABLE UCSR0B &= ~_BV(RXEN0);
#define RX_ENABLE UCSR0B |= _BV(RXEN0);
void setup() {
XIAOMI_PORT.begin(115200);
....

The 2nd Communcation will be a problem, because it is serial also?
If yes, is there any solution/library for BLE communcation solution?
Are the TX/RX pads not useable?
But they are linked/used when connected to PC via USB too, then it should work too for this, or is BLE disabled when conntected via USB?

I'm a little bit confused.
Thanx for any clarification