Mindthegapps is just official google apps with no modifications, so even if what you're saying is true, then your issue is google apps. How did you deduce that mindthegapps leads to slower video loading times? So installation of LOS without gapps runs fine? Then the choice of your ROM is not the issue here.
Make sure you are connected to the right port. I have a USB c cable and faced the same issue. Turns out I was connecting to the power port not the data port (not sure how to explain it better).So if i connect the OP8T with this rom to my PC it now only charges. All other options on the USB menu on the phone are greyed out. Windows also doesnt recognizes it, USB debugging is on, drivers are there (i installed the ROM via this laptop) What can i do, i want to transfer data from the phone to laptop and later flash another ROM, but cant connect