Question about foam fly fishing.

First I want to say hello to all of you roffians.

I will just start with a little presentation as I am new to this NG.

I am lurking on this group episodically since 1 year now.
I am living in France, and am quite newbie to flyfishing, although I
went trough my first season quite successfully.
I fish trout since I am 5 or 6, but with other techniques.
I have to say I was always interested in fly fishing, but I never dare
go into it until last year.
But since last year all my rods but the fly rod never went out of the
garage...

So here is my question, I can see many foam patterns on the net.
Some are really impressionistics.
I know they can be real killers on bass, even if this is not my common
specy around here.
But what about fishing trout with them?
Arounf here I mainly have brown, and some rainbows, but rainbows are
mainly introduced to help with the fishing pressur.

I tried the experience to tie 2 of them, one in foam, the other with
Pheasant biots and Helk hairs.
The "natural one" made some brown go on it (without taking), maybe a
smaller pattern would have been successfully catching.
The foam one even affraid them when sight fihing.

So my question is, do these foam fly catch trout?
If yes, can it be possible in some geographies they would catch and in
other just make the fish laugh?

And why?

Thanks for reading this long thread.