Is this possible to do this in any easy way? Group node only have option to group points for some reason, but in my case i want to test geometry that doesnt have lot of points,but have big faces!
So only solution i figured is to remesh my geo to have higher point density do the group,flood fill expand selection,promote it and then group transfer it to the original set of geo.
Feels like a lot of not necessary calculations!
The very best would be also have a threshold too if its in just a tiny bit in my bounding gro dont group it then.
Anyone,any idea?

Just use a group promote after, from pts to prims. That is the easiest

that's sad if that's true, but thanks for your answer

Group promoting may not help if the faces are so big that the bounding geo doesn't contain any points and just intersects face

In that case you can use Boolean SOP in Detect mode

Using group promote is a fast way but if you want to check, if every single point of the surface is inside a geo, you probably need something like boolean and compare the area between the the faces. If the areas are equal the geometry is completely inside.

Here is an example