honestly it really depends on the Betta... I've had some that like playing in the flow and I've had some that hate and type of flow...I actually had one guy in particular that is there was any flow whatsoever he would flatten himself on the opposite side of the flow and refuse to move.
So if you definitely want a betta in there it's better to get one and adjust to that particular betta accordingly
or you could go with a female or plakat - shorter fins so less resistance.
Much luck! Post pics of your guy once you get him!