How to print a Variable in TFT 3.5 in with the MCUFRIEND Library?

Other Hardware Displays
2

All Print.h style print methods just take values of different types e.g. String, int, float, ...

If you require to change the print position, use a separate setCursor() e.g.

void Imprimir_Voltage_CFE() {
    tft.setTextColor(RED);
    String ValorV = String(vrms);
    ValorV.toCharArray(vrms_1, 4);
    tft.setCursor(190, 120);
    tft.print(vrms_1);
}

Note that there are far easier ways to do evaluate the voltage and do the printing.

Personally, I would write a helper function that formats the voltage, draws a fresh background, prints the new value of the voltage.

David.