A Bastard or Longsword could be a primary or a secondary weapon, based on the preference/training of the individual. Against a lightly armoured or unarmoured foe, a cut or thrust would be capable of killing or seriously wounding. Against an armoured foe, half-swording or a murder stroke (holding the sword by the blade and using the hilt as a club) could penetrate or damage armoured plate, though this to would vary based on the metal from which the armour was made and it's thickness. A mounted man-at-arms would likely dispense with his Lance first, during a charge, while a dismounted man-at-arms would probably start out with a poleaxe or another polearm first, before utilizing their sword. This would certainly be the case from the 14th century onwards, with the widespread emergence of plate armour.

John Clements book Medieval Swordsmanship is a good read, and there are a number of Historical European Martial Arts websites on line that have pdf copies of Medieval/Early Modern Fighting Manuals, if you want to get a sense of how contemporaries would have utilized their weapons.