The specs of the Swag 2 list Voltage Output of up to 80W, but they make no mention of it's voltage output range, nor do they mention what resistance you must be at to achieve this 80W - so I suspect has no voltage boost circuitry.

If that is the case you are at the mercy of the battery level, if you need higher voltage to be sent to the coils than is currently in the battery to get the wattage you need you're screwed and the vape will get progressively weaker once the battery is below this level.

Bear in mind the mods board receives the voltage the battery has, and the more Voltage it has the higher power levels it is capable of providing - the board either reduces this Voltage (using a buck chip) if you have selected a lower power setting than the battery is capable of supplying, or, if you select higher than the battery has a sufficient voltage to provide it must have voltage boost circuitry to achieve this. Wattage is just a convenient method of describing the power levels (Volts x Amps)

The only way you can combat reducing power levels in a mod without a voltage boost chip is to use lower resistance builds as a lower resistance build pulls more Amps from the same Voltage level, and Volts by Amps = Watts, you can achieve higher Wattage. But you MUST use batteries with a high enough Amp rating (this applies to every vape mod).

Unfortunately this means you need to pull out your calculator and work out what resistance is needed to provide the Wattage you need when the power is getting low so it can provide this power level for the majority of the battery charge.

It sounds confusing but a mod doesn't pull Watts from the Battery or send them to the 510 - it is all down to the voltage level of the battery and the Amp rating (how much current the battery can provide safely) - if it doesn't have voltage boost circuitry.

In other words regulated mods without boost circuitry are a bit shit, with a 20C Boost Chip added to the board you wouldn't have to constantly refer to Ohms Law and adjust your builds.