They work for sure. However there is a super weapon 'power-up' that will go until it ends, no need to switch it because its the best weapon in the game, and is temporary. Also you need to have ammo for the other weapons, and you will need to purchase the other turrets first to use them.

The Abilities work too, but you have a limited number and may need to purchase more at the upgrade screen. Some like the repair wont work unless you actually need repairs. The force-field needs to be bought then it needs energy to run. The energy recharges over time (the blue bar) - you can upgrade the recharge amount.

Its an outpost with limited supplies/ammo - you can buy more between battles. If you run out of ammo in a fight, you can call in a supply drop with 'S'. You can also repair your shields, if you have a repair kit, with '9' or '0'. Block damage with your force-field, if its upgraded and has energy with 'Spacebar'