If I was to switch from Bt to another bt openreach ISP such as Sky or Plusnet or Zen broadband, would i be connected to a different line from the cabinet to the exchange? Would I see any difference in connection ie Online gaming improvement or would everything just remain the same and theres no change at all?
It would be just the same line from the cabinet to your exchange. Speed may be slightly different, but I cannot see anything else changing.
It would be best to make sure you do not have any issues with your current connection, like noise on your phone line, which will cause problems.
See your existing thread https://community.bt.com/t5/BT-Fibre-broadband/Bt-Infinity-congestion-causing-gaming-lag/m-p/1911205
The first thing that happens with a switch between any provider be it BT to SKY etc or the other way around, SKY to BT etc is a cease and desist is placed on the port at the cabinet.
The new ISP will then place an order for provision, if there is a waiting list on the cab it will go in the queue and you will be provided when a place becomes available.
This is yet agaiin an uniformed rule made by OFCOM among many they've made. Just make sure that whichever ISP you intend to move to guarantees there is no waiting list on your cab. They can check with BT Wholesale but frequently do not.
Other than that everything will still be the same.