Touma should be able to beat Subaru without much trouble in one or two punches. Given their ranges the two should start a few meters apart, so Touma crosses that distance and punches out Subaru's lights out in a few seconds, likely not giving him the chance to use much of his powers.
As for Beatrice, given that Subaru doesn't have summoning listed as an ability, do you mean that he can summon her mid-battle or is that like a bonus round where she's helping him from the start. 1st option won't matter since Subaru very likely loses before he has a chance to summon her, and in the 2nd Beatrice would probably stomp Touma in melee due to speed advantage, making Subaru irrelevant to the battle. But since it would make it 2v1, it wouldn't be a valid battle.