Raspberry Pi 4 8GB - 2 USB Cams - C++ not loading but JS loads video in browser

I have Raspberry pi 4 with 8GB ram, I have connected two USB webcams (Eternico Webcam ET101 HD) to it, I need to read video from both cameras at once for triangulation of detected objects.

I am using C++ code from OpenCV docs: https://docs.opencv.org/3.4/d8/dfe/classcv_1_1VideoCapture.html

#include <opencv2/core.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
#include <stdio.h>
using namespace cv;
using namespace std;
int main(int, char**)
{
    Mat frame;
    //--- INITIALIZE VIDEOCAPTURE
    VideoCapture cap;
    // open the default camera using default API
    // cap.open(0);
    // OR advance usage: select any API backend
    int deviceID = 0;             // 0 = open default camera
    int apiID = cv::CAP_ANY;      // 0 = autodetect default API
    // open selected camera using selected API
    cap.open(deviceID, apiID);
    // check if we succeeded
    if (!cap.isOpened()) {
        cerr << "ERROR! Unable to open camera\n";
        return -1;
    }
    //--- GRAB AND WRITE LOOP
    cout << "Start grabbing" << endl
        << "Press any key to terminate" << endl;
    for (;;)
    {
        // wait for a new frame from camera and store it into 'frame'
        cap.read(frame);
        // check if we succeeded
        if (frame.empty()) {
            cerr << "ERROR! blank frame grabbed\n";
            break;
        }
        // show live and wait for a key with timeout long enough to show images
        imshow("Live", frame);
        if (waitKey(5) >= 0)
            break;
    }
    // the camera will be deinitialized automatically in VideoCapture destructor
    return 0;
}

Problem is when I try to load video from both cameras at once, whole video stream just frezzes and I have to kill it.

I tried to use python code for OpenCV, but with same behaviour.

I ran it as separate processes, just with different deviceID -> not working (The first camera opens correctly, when the second tries to open it freezes and I have to kill it)

I also tried it like this: https://stackoverflow.com/a/13926879/17053282 -> not working - same as above

After searching for answers I found out that problem could be related to USB bandwidth, but.. Interesting is that when I tried to load video using JS in web browser it works perfectly fine. Screen below..

Live video from both cameras displayed in webrowser

Any ideas what could be wrong? Or how to run it in C++?

Goal: I need to read video from cameras simultaneously, and stream it over network in C++.