Do you think if I get external microphone and turn OFF physical audio OR lower it that I won't get feedback form the video sources if the microphone is not too close to the speakers?
You're getting into the same world as a live concert. All sorts of other sounds in the air, that you don't really care about in that particular mic, but the mic doesn't know any different. It just measures the total air wiggle in that location, with no more smarts than that.*
So, just like a live concert, you put each mic right up close to the sound that it's supposed to pick up, so that *that* sound drowns out everything else. But even so, every mic still has everything in it, just in different proportions. The bleed from something else is usually low enough to be drowned out by both the intended sound and the actual intended mic for the other sound, so it's fine for a live PA.
But sometimes we still need to block sound on stage. If you've seen some clear plastic disks around a drum set, for example, those are called "shy baffles". Their purpose is to block the direct path for the cymbal sound into the vocal mics. If you insist on having live speakers and a live mic for your rig, you might need to do something similar.
With a large acoustic space, like a concert stage, just those baffles are usually all that's needed because the other paths are so long and lossy that it hardly matters. But if you're in a small room, then the reflections off the walls, ceiling, furniture, or whatever could be a problem too.
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* Actually, the direction matters too, but not as much as you might think. A "cardioid" mic, for example, has a null - no sensitivity - at the back, and that null is often pointed at the closest "floor wedge" speaker on stage, to reduce the tendency to feed back. (the increasing ring that sound systems do when they're turned up too high) But a cardioid's sensitivity doesn't drop off very fast until you get close to that null. In other words, the null is pretty sensitive to direction.
A "figure 8" mic has equal sensitivity in front and in back, and a "ring of null" on the sides. Also sensitive to the exact direction, so if something comes in just a little bit off of that null, you still hear it.
"Supercardioid" takes that "ring of null" and moves it towards the back, but not all the way back to a point like a cardioid does.
"Omnidirectional" is equally sensitive everywhere, with no null at all. Small mics are forced into this, just because of their size. You have to compare over some physical space to tell direction. Headsets and lapel mics are often omni for that reason, and rely solely on relative distance to reject other things...which doesn't always work.
You can point the null at the worst offender, and use that to clean things up, but don't forget that a reflection will come in from a different direction. The mic will still pick *that* up. And if you have *two* major offenders (stereo speakers, perhaps?), then it might be tricky or impossible to put *both* of them in the mic's null, even if you did choose the mic for its pickup pattern, and specifically where that null is.
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