any advice on integration systems?

I am a stylist who works with integration systems, and I have worn one myself, a time or two.

For long hair styles usually they don't work that well unless they have a skin part area built in it.  I say that because most long haired people don't wear their hair very fluffy on top, and therefore you need a part line.  Well, for long hair styles, the integration doesn't allow you to have the look of a natural part line, so therefore in my opinion it can look wiggy.

For shorter haired women who want a lot of top volume and where you don't see a visible part line in their hair, then they work great.

My own hair is very fine and thin, so for fun I custom designed myself an integration system.  I told the factory to put a left side skin part in it, so I could mimic the look of a part line.  I tried 'off the shelf' integrations without the part line design, and I felt too self conscious, like it looked fake.

So, if you are wanted a long hair look, than you may have to get a custom made system.  As for companies, I am licensed, so I deal directly with the manufacturers, not retail establishments, so I can't help you there.

Good luck!