The Bussard collector, also known as a Bussard ramscoop or ramscoop, was a device usually attached to the forward end of a warp nacelle. The Tosk variation of the Bussard collector was known as the arva node. The collector, along with the Bussard collection coil, was called a Bussard unit. (TNG: "Silicon Avatar", okudagram; DS9: "Captive Pursuit")
All Federation starships were equipped with Bussard collectors, which were positioned in the best line of sight to collect interstellar particles. Collection worked best in regions where particle density was high, such as in star systems or nebulae. The Bussard collector normally collected hydrogen, especially deuterium, for fuel replenishment, but could be reconfigured to collect various gases like sirillium and plasma particles. A Bussard collector could also be reconfigured to expel gases or plasma. (TNG: "Samaritan Snare") Bussard collectors were not capable of producing nadion emissions. (VOY: "The Haunting of Deck Twelve")
Aboard the Galaxy-class USS Enterprise-D, in the Engineering Systems Database, there was a folder titled "Bussard Collection Field Operations". This folder contained technical manuals relevant to the topic. (TNG: "Booby Trap", okudagram)
I owned the TNG Enterprise engineering manual years ago and if memory serves, it stated that the goal was to collect atomic hydrogen or deuterium when available. The quantities available were never adequate to completely replenish a starships tanks inflight, but the option of passing into a nebula gas cloud or the like certainly would.
The pics below contain too much info to relay so I included them.
Here are the links to the above images
Follow this link for the actual Technical manual. The link opens to the section where you can read exactly how the Bussard collectors work. They are in-fact effected by the warpfield at speed.
In specific detail to the OP's question:
works in close connection with the main navigational deflector.
In normal operation, of course, the job of the deflector is
to prevent any interstellar material from contacting the ship.
Small field "holes" are manipulated by the deflector and MFG/
C to permit usable amounts of rarified gas through.
Source: Technical manual