well i have a lot of questions about portals, i made a few ones and they work perfect(this was in normal area), now when i get to the hard and open area of my map i start to have a few questions.

1)_ clip can "cut" or break portals?
2)_ clips can help me to get portals working if i use them as a "structural brush", idk if i say this perfectly but here is a image(this portal area work perfect):

whats going to happen if i replace that brick texture(work as glass in this example) with a clip texture, the portal will have leaks?

i ask this becuase in some parts of my maps fps go from 90 to 30 

There is probably a tool texture with the properties your describing.(Sealing a portal with a structural/transparent texture). I've never needed it though so we might do portals differently.
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If the clip is working to seal your area and doesn't cause any lag I would keep it. I might use that method myself if it comes up and I couldn't use a caulk brush or blue texture.
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you can also use the hint/skip texture to divide your map into areas. Then portal on either side of the hint/skip brush. Its not as clean as portals but is good for large outside areas.

clips dont matter if they go trough or not in portals while being DETAIL
non colliding / and weapon_clip can go on both sides too only downside is they get rendered in both zones
(but not like you going to have 5000 brushes trough the portal anyways)

As far as I am aware the clips can not be used structurally to make the portal (  tested it in radiant ).

I use some structural caulk to portal outside areas just placed so not to block any player / Ai paths .

well i tested and clip work as structural for portals.

thanks to allthe people that answer this topic

(i dont going to select the best becuase all the replies are valid)