I had various experience vs various players:
- Khamrakulov: Tarrasch (Condom)
- Prie : Advance (rapid Naujac and simul night Montreux)
- Fressinet : Exchange Winawer
- Nataf : Exchange Winawer (simul)
- Tirard : Exchange Winawer
- Kosten: Advance with a dxc5 (rapid long time ago Rodez)
- Lau : Tarrasch
- Santo Roman : Winawer
- Juglard : Mc Cutcheon
- Cornette : Tarrasch Nf4 (he was very young at this Bordeaux rapid tournament)
- Renet : Winawer (simul ET)
- Donchev: Winawer classical with ooo for black (blind simul)
- Nepeina Leconte: KIA (simul)
- Olivier Leconte : Mc Cutcheon Be3
- Safranska Anda : KIA
- Boudre : Tarrach main closed line
- Pareira : KIA (simul CEIT...he was very young at that time)
- Marciano : Tarrasch
and so on
What is clear for me is a good player usualy sticks to main lines or positions he likes to practice ... because he has NO obvious reason to choose a dubious opening vs a low rated player.
I played only one time 2-knights variations in Budapest vs hungarian player...he knowed like me old game from the 1970's....Spasky game.
Tarrasch Nf4 was played vs me at nice by a low rated player (maybe 1800 Elo) at Nice tournament: somebody told him it was a good off-beat variation against the closed main line Tarrasch...but no lucky, I was enough experienced at that time to know what to do as Black. Same with young Cornette, he played this line and after the usual exchange sacrifice I won with my pawn center. Sometimes result of a game is not decided by knowledge of the opening moves...but just the plans at the end of the line written in the books. If you didn't work yourself on other games...you have done only half work.