Phantasms and Illusions

having a bit of trouble understanding how they work. here are a scenarios that occurred.

players are in trench warfare attacking catapult positions, protected by archer nests located behind them. the archers are keeping the party tied down. so the illusionist casts the illusion of a brick wall, between the archers and the party, blocking LoS. my understanding of the rules are, there is no RR, just a basic spell roll to see if it fails. not using any optional rules yet. the spell succeeds and a brick wall appears between the groups. now, the party KNOWS it is an illusion, but will they need to actually go up and touch it (try to) to determine it is an illusion and be able to return fire at the archers. what confuses me here is that the illusion does not dispel, so does the player see thru the wall to shoot at the archers? as far as the archers go, a brick wall just suddenly appears, how do they KNOW this is NOT an illusion. i mean, walls just do not appear out of thin air. so when is the illusion, not an illusion any more?

another example of game play was, the illusionist casts an illusion of a broken mirror shards, adds the light sense to it, then places it around the head of an opponent, thus causing them to see multiple reflections and hampering their ability to move and combat.

in the 1st EG, i had an archer run out to inspect the wall, he goes to touch it, hand goes thru, so the archer now knows the wall is not there, but the illusion persists. so can the archer see thru it now? what about the other 2 archers back in the weapon pit? do they need to go touch the wall, or does seeing the 1st archer stick his hand thru the wall identify it as an illusion? again, does the illusion persist, even though it is known to NOT be an illusion?

in the 2nd EG, how is determined it is an illusion? the sense is light, not touch. or does the failure of being able to touch one of the shards of mirror dispel the ENTIRE illusion, or just that particular shard? i mean, there are 40 shards of mirror floating around their head. would they need to touch each one?

for any one else who has questions about illusions and phantasms, i found the following resources, since no one here seems to know any thing about them.

https://www.starjammersrd.com/magic-and-spells/

REALLY dos a good job of explaining them. i learned that even once an illusion is known, it still is visible as a translucent outline. among other things.

According to RMC, the actually 'sense aspect' is created. It doesn't matter if you know that it is an illusion or not. Even if you stick your hand through a Light Mirage, you will still see it. RM2 says pretty much the same.

It's your game though, and if you want to allow folk who realise that it's an illusion to see through it then that sounds fine. As long as you're consistent with your interpretations in your game that that's fine.